Played on Legendary a couple of times
Jaime Griesemer, designer on this game and a lead designer for Halo 2 and 3, has a decently well-known quote about the sacred 30 seconds of fun. Essentially, take 30 seconds of gameplay, make 'em good, and then stretch that across the entire game. This could be cynically interpreted as a way of excusing Halo's heavy asset reuse, especially in its first two installments, but my understanding of this quote is that the 30 seconds are not set in stone. Contained within those 30 seconds are a stupid high number of possibilities, According to Griesemer, “if you don’t nail those 30 seconds, you’re not gonna have a great game”. Halo nails the thirty seconds by allowing so many things to happen within them.
The primary way it does this is through its AI and enemy design. Let's just imagine an encounter with an Elite and three Grunts. In Halo, killing an Elite makes all the Grunts scatter and stop shooting. This is nice for saving ammo since you can just go and melee the Grunts, so the risky and rewarding strategy is to ignore them and their potential damage entirely and just shoot the Elite. What seems like a simple tradeoff is anything but binary, since killing an Elite with self-preservation AI and a beefy shield is rarely that simple. Maybe you shoot one or two of the grunts so you can poke your head out longer and give yourself more time to kill the Elite, but this spends ammo. Maybe you melee those grunts and retreat, saving the ammo and making the Elite killing easier for yourself, but that's not always feasible because sometimes you get shot in this game. Maybe you just blow them all up with a grenade (you probably do), but if you do, you probably wanna be efficient by blowing up a clump, or sticking an Elite (which is hard unless you're like me and just so good at games
Depending on where each of these enemies as well as any cover is placed, the execution of any of these plans changes. For example, the enemies may not be in a clump for the grenade to work. Not only are they capable of flanking your cover spots (which can be rough given Chief’s movement speed), but they might do so from multiple angle (especially if the cover is thin), complicating things and forcing you to make quick decisions about who to shoot and aim well enough to execute them. Maybe all the enemies are grouped together, great for not just grenades but also dodging projectiles. Maybe they lose sight of you so you pop out the other side and get a few valuable shots in. Maybe you don’t pop out and instead wait for them to come to you, which often does result in clumping (also Jackals will move their shields out of the way for headshots). If they're further away, meleeing is impossible, you have to calculate the grenade throw arc, shooting is more precise, Jackals are much harder to get a good angle on, and enemies are more than content to just sit behind cover, with Elites especially happy to get their shields back (but dodging is easier)!
The AI's sense of self-preservation goes a long way in encouraging more aggressive play, and rather than constantly moving straight towards the player, their often zigzaggy movement and ability to roam arenas freely organically sets them up into these different positions. Sometimes they do it on their own, and sometimes they do so more predictably when they're in your sightlines and do a canned dodge animation. RNG does play a part in how a firefight plays out, but it's offset by the existence of more predictable behaviors, and the outcomes decided by RNG are rarely 100% good or bad. For example, an enemy randomly choosing to move behind cover means you can't shoot him, but he also can't shoot you. You also still have a good idea of where he is (y'know what this game is really missing is teleporting enemies) and what he may do next. Put just one rock in the arena, and the player now has the choice to shoot a Grunt and remove that threat from the equation, or use the cover to do so temporarily. The player is constantly asked to assess their threats and change their targets accordingly, with priorities shifting a bunch in just a few seconds.
The focus on AI also highlights how good grenades are as a mechanic. Obviously efficiency and satisfaction in blowing up clumps of Covenant is fun, but they can also be used to predictably trigger dodge animations and make enemies stop shooting for a few seconds. You can exploit this behavior to reposition, buy yourself just enough time to get your shield back, or flush enemies out of cover and give yourself some time to shoot (or throw another grenade which usually kills them but it does have higher cost!). You can even force them off cliffs but lose their weapon as a result. All of the strategies in this paragraph arise from a secondary interaction that grenades have, not even the main purpose of the damn things, which is really the magic of Halo: tons of complex, cool outcomes from simple mechanics. Another example can be seen in hitstun, which always happens on Grunts, up close against Jackals, and vs. unshielded Elites. This gives your guns a second interaction to just damage, opening up strategies like distributing fire to lock down multiple Grunts or circling around Jackals.
All of the strategies in all of the above paragraphs can arise from giving the player a gun and some grenades, throwing them into an arena with 2 enemy types and a rock (and indeed you will have to share it). This is because video game variety doesn't have to come from the presence of a lot of ideas, but the depth and nuance of ideas that already exist. A grenade is only one thing, but look at how many different ways it can be applied! Now see how everything in the encounter changes if you give the player a rocket launcher, or add a second Elite so getting the grunts to scatter is harder, or maybe add some Jackals to make the scatter phase more complicated, some more cover so the player has to balance strafing to avoid fire with using said cover, put a Banshee and make them choose between constantly evasion and high-cost destruction, or put some dickhead Wraith on the player’s ass across the map, constantly forcing them to reposition.
This baked-in approach to variety is how Halo can get away with having 4 and a half unique arenas and 7 enemies (not counting vehicles or popcorn flood). Each encounter can play out differently even if the arena, enemy placements and composition are the same (and even moreso when they ARE different). It's not ideal to reuse the same circular arena 40 times, but in a game with such varied outcomes it's not quite the end of the world. The core systems do a lot of the heavy lifting, which I might be biased toward given how interesting I find such things. As always in a shooter, aiming is going to be the key factor. If you noscope headshot an Elite, you can get away with otherwise boneheaded positioning choices. A player with great aim can go through with less solid plans, while missing a shot can force you to readjust your plan. If you take too long to shoot that Jackal, the Elite approaching from behind might make your life a lot harder. If you couldn't tell, positioning is quite important too, and arenas often spread cover far enough apart to where changing your position is not done easily. If a Random Enemy is Approaching, do you run away and risk taking more damage, or do you stay put and bet on your aim and dodging skills? (Notice how the RNG makes the game more dynamic by working in tandem with the skill checks). Do you run into a group of Grunts faithful that you can stunlock and punch all of them? Or do you let them live longer and possibly take unfavorable positions such as attacking from multiple angles, which makes dodging much harder. Aiming and shooting is a basic skill check with a very binary outcome (you hit 'em or you don't). It's exceedingly simple on its own, but when the game has so many variables that are always changing states, like those examples of both you and enemies' positionings, but also their current behaviors, ammo counts, your shield and theirs, weapons on hand and on the floor, etc. Each passed or failed test has a butterfly effect on the whole encounter and your own gameplan. RNG is also a simple way to achieve unpredictable results, but it too is complimented by these states (for example, that earlier Random Enemy Approaching situation will probably trigger a different response in you if you only have a quarter shield left as opposed to full). Overall, the core mechanics of Halo are quite-well considered, creating consistently deep combat!
The only thing Halo really does wrong on a foundational level is the healthbar. The regenerating health itself is good, mitigating the frustration of getting shot from offscreen but still punishing the possible bad positioning that lead to it, and encouraging COOL people to get good at dodging and aiming so they don't have to wait for their shields to come back all the time. The longer recharge and higher shields lead to prolonged consequences as well, where you might see guys coming on your radar and realize you'll have to fight them with less shield than you'd like. Since enemies in Halo can move behind you randomly and dodging every projectile just isn't feasible, it makes sense for the game to not give permanent consequences for getting hit. This is offset by the actual healthbar underneath, which does not make sense for the game and often leads to more waiting behind cover like a loser or restarting on the slightest mistake to avoid permanent damage. On its own it's not necessarily bad, but combined with the game's checkpoints it kinda (really fucking) sucks.
The checkpoints are also more than willing to put you in a section with red HP, emulating the worst of F5 to save anywhere systems. In old PC games, sometimes it's better to go back to the last encounter and do it better so you have a better chance in the current one, and here you don't even have the choice. The healthbar does offer connective tissue between encounters, but the two weapon limit and AMMO also do that in a much more interesting way that results from your choices, and not getting clipped by a couple of needles from behind.
That two weapon limit is great at coloring encounters differently as well, encouraging strategic decisions but never railroading to the point of turning encounters into puzzles and removing that sweet sweet depth. You could run through Assault on the Control Room with the Rocket and Sniper, even if it is a tactical decision so poor it would put Reach Brutes to shame. The game feels designed around the Plasma Pistol, with it being the most common and versatile. It works against all three enemy types, but the nuance is that you have to charge it to remove the shields. Since you give up the ability to remove even Grunts through kills or stun, it's risky! Of course you can do it from behind cover, but it's worth noting that the charge shot's chance of hitting drops off with range, especially in the more open arenas, and especially especially against Elites who just love to dodge the thing. Here we see that weapon effectiveness against enemies isn't always straightforward, affected by range and level design. You might be inclined to use a Plasma Rifle instead, which too murders Grunts and works well on Elites, but can be rather unreliable against Jackals unless you get close enough to circle the assholes.
The Magnum, the best gun ever, is often found accompanying its fellow pistol. On its own, it's far from the best against Elites and inconsistent against Jackals. Your go-to isn't a single weapon, but instead a combination, which you are given reasons to abandon. You could run low on ammo, you could find a power weapon, you could be playing a fuckin' flood level. Although it might seem better to have every weapon be the same level of viable, there's arguably something gained through not adhering to that. Power weapons like the Rocket and Sniper demonstrate this quite well, since their limited ammo means every use of them is high-cost and a big deal, and running out can lead to some great "aw shit" moments. The same can be said for something like the Needler, which generally sucks but can be used in a pinch. Killing a Grunt and taking it from him to stick an Elite as you cut off his cover routes is fun, the knowledge that its more situational and less generally reliable making those scrappy strategies more satisfying.
The Flood are quite stupid, both in their design and quite literally. Their straightforward behavior doesn't really lend itself to any of the strengths listed above. It makes sense why Flood wouldn't take cover or react to their fallen brethren in any way, but it still sucks. Making the Shotgun into their obvious go to isn't bad inherently, but unlike the plasma pistol it's actually the obvious best option on its own. Thinking about your secondary against the Flood is like thinking about what color underwear you're gonna put on. Since the enemies aren't particularly fun, trying to run a sub-optimal loadout against them would be a great way to make yourself hate reloading and slow movement speeds. They're also often paired with CE's worst level design sins: reused hallways that barely feature any interesting cover, usually one-way crevices which lead to hiding inside instead of gliding between. What about hallways as opposed to more circular or open arenas that give the player and enemies a more complex relationship with the environment? Stupid wave defense sections where enemies flood in from one choke point so you never have to think about anything too complex, everyone's favorite! They even hit you with the combo of locking you into these sections! Their more frantic, charge-heavy nature puts the player on the backfoot in the way the Covenant never did. They start off very stimulating and refreshing, but quickly give way to tedium. They’re too reactive, not proactive or tactical enough in a game that otherwise nails that balance. The focus on fast decisions over complex ones gives them very little longevity, and ultimately become far more exhausting than if there were just 5 more Covenant levels. On the bright side, once the other enemy types are reintroduced, encounters become good again, even introducing new strategies like waiting out the infighting and kiting enemies into certain areas to spark it.
Still, pacing is one of those aspects that defines the "game", the part built on top of the mechanics and systems and creates the holy holistic experience, the sum of the parts. The Library would be a great example of a colossal failure in this department, since it fails to distract from (and in fact takes 10 megaphones to tell you all about) the shallowness of the Flood. Common criticisms of Halo tend to be aimed at this experience, with many claiming the lack of visual variety just makes them not wanna play the thing. Can't say I blame anyone who got fatigued with the game, I used to feel the same way, but I just don't anymore. Of course better pacing would be appreciated (I often skip the Library now), but surely in a game whose foundation lends it such diverse, dynamic gameplay, it's not the most important thing. Of course I'm biased because the best parts of Halo 1 are the parts I find most interesting in 99% of games, because at some point you skip the cutscenes and stop seeing the game for how it looks.
Despite some clear missteps, Halo is a wonderful game. In a word it's dynamic. Let's take Hunters as a sort of counterexample. Most people don't think they're anything special since you can employ a pretty one-note strategy of baiting out an easy attack and shooting them from behind. This is lame because it's not really a decision, it's a formality. You've solved the Hunter problem, permanently. Thankfully the bulk of the game is not Hunter encounters. Halo rejects formalities for ever-changing scenarios, leading to consistently engaging, good-ass decision-making. If you imagine each encounter as a 30 second bubble that represents everything that could happen, that bubble is reeeeaaaaaaallllllllly big. Add up every complication that can happen in 30 seconds of Halo, and you get a game that’s fun for hundreds, maybe even thousands of hours. Player creativity can arise from mini-situations that the developers probably never saw coming themselves. You can't solve the game if it's creating new problems on the fly. The game creates a ton of complex situations to work through, and all out of mechanics that are intuitive and simple to parse (tech skill is awesome, but the game's situational depth proves its not necessary to be a sick game). The mechanical foundation is so robust that the developers managed to build the ugliest building on top of it, and it still works better than most games I've played.
Saying Halo 1 has a ton of variety probably sounds like a stretch to most, but don’t be fooled by the visually repetitive exterior (ironically more common in the game’s interior rooms). Firefights may not look different, but they play different. Enemy variety is often made out to be important for variety's sake, but Halo shows the truth in quality over quantity. Hell its biggest flaw is not sticking to that all the way. While there is value in the things Halo lacks (even I sometimes do the Banshee skip in Assault), it serves as proof that flash, polish, and high production values need not be the priority of video games. Halo more out of 3 good enemy types than most games can with 5x as many. Its limited content and surface variety is a footnote compared to what was achieved with its gameplay. It's a shining example of a game that's so varied and replayable not through content, but through the gameplay systems. Put simply, real ass video game.
Jaime Griesemer, designer on this game and a lead designer for Halo 2 and 3, has a decently well-known quote about the sacred 30 seconds of fun. Essentially, take 30 seconds of gameplay, make 'em good, and then stretch that across the entire game. This could be cynically interpreted as a way of excusing Halo's heavy asset reuse, especially in its first two installments, but my understanding of this quote is that the 30 seconds are not set in stone. Contained within those 30 seconds are a stupid high number of possibilities, According to Griesemer, “if you don’t nail those 30 seconds, you’re not gonna have a great game”. Halo nails the thirty seconds by allowing so many things to happen within them.
The primary way it does this is through its AI and enemy design. Let's just imagine an encounter with an Elite and three Grunts. In Halo, killing an Elite makes all the Grunts scatter and stop shooting. This is nice for saving ammo since you can just go and melee the Grunts, so the risky and rewarding strategy is to ignore them and their potential damage entirely and just shoot the Elite. What seems like a simple tradeoff is anything but binary, since killing an Elite with self-preservation AI and a beefy shield is rarely that simple. Maybe you shoot one or two of the grunts so you can poke your head out longer and give yourself more time to kill the Elite, but this spends ammo. Maybe you melee those grunts and retreat, saving the ammo and making the Elite killing easier for yourself, but that's not always feasible because sometimes you get shot in this game. Maybe you just blow them all up with a grenade (you probably do), but if you do, you probably wanna be efficient by blowing up a clump, or sticking an Elite (which is hard unless you're like me and just so good at games
Depending on where each of these enemies as well as any cover is placed, the execution of any of these plans changes. For example, the enemies may not be in a clump for the grenade to work. Not only are they capable of flanking your cover spots (which can be rough given Chief’s movement speed), but they might do so from multiple angle (especially if the cover is thin), complicating things and forcing you to make quick decisions about who to shoot and aim well enough to execute them. Maybe all the enemies are grouped together, great for not just grenades but also dodging projectiles. Maybe they lose sight of you so you pop out the other side and get a few valuable shots in. Maybe you don’t pop out and instead wait for them to come to you, which often does result in clumping (also Jackals will move their shields out of the way for headshots). If they're further away, meleeing is impossible, you have to calculate the grenade throw arc, shooting is more precise, Jackals are much harder to get a good angle on, and enemies are more than content to just sit behind cover, with Elites especially happy to get their shields back (but dodging is easier)!
The AI's sense of self-preservation goes a long way in encouraging more aggressive play, and rather than constantly moving straight towards the player, their often zigzaggy movement and ability to roam arenas freely organically sets them up into these different positions. Sometimes they do it on their own, and sometimes they do so more predictably when they're in your sightlines and do a canned dodge animation. RNG does play a part in how a firefight plays out, but it's offset by the existence of more predictable behaviors, and the outcomes decided by RNG are rarely 100% good or bad. For example, an enemy randomly choosing to move behind cover means you can't shoot him, but he also can't shoot you. You also still have a good idea of where he is (y'know what this game is really missing is teleporting enemies) and what he may do next. Put just one rock in the arena, and the player now has the choice to shoot a Grunt and remove that threat from the equation, or use the cover to do so temporarily. The player is constantly asked to assess their threats and change their targets accordingly, with priorities shifting a bunch in just a few seconds.
The focus on AI also highlights how good grenades are as a mechanic. Obviously efficiency and satisfaction in blowing up clumps of Covenant is fun, but they can also be used to predictably trigger dodge animations and make enemies stop shooting for a few seconds. You can exploit this behavior to reposition, buy yourself just enough time to get your shield back, or flush enemies out of cover and give yourself some time to shoot (or throw another grenade which usually kills them but it does have higher cost!). You can even force them off cliffs but lose their weapon as a result. All of the strategies in this paragraph arise from a secondary interaction that grenades have, not even the main purpose of the damn things, which is really the magic of Halo: tons of complex, cool outcomes from simple mechanics. Another example can be seen in hitstun, which always happens on Grunts, up close against Jackals, and vs. unshielded Elites. This gives your guns a second interaction to just damage, opening up strategies like distributing fire to lock down multiple Grunts or circling around Jackals.
All of the strategies in all of the above paragraphs can arise from giving the player a gun and some grenades, throwing them into an arena with 2 enemy types and a rock (and indeed you will have to share it). This is because video game variety doesn't have to come from the presence of a lot of ideas, but the depth and nuance of ideas that already exist. A grenade is only one thing, but look at how many different ways it can be applied! Now see how everything in the encounter changes if you give the player a rocket launcher, or add a second Elite so getting the grunts to scatter is harder, or maybe add some Jackals to make the scatter phase more complicated, some more cover so the player has to balance strafing to avoid fire with using said cover, put a Banshee and make them choose between constantly evasion and high-cost destruction, or put some dickhead Wraith on the player’s ass across the map, constantly forcing them to reposition.
This baked-in approach to variety is how Halo can get away with having 4 and a half unique arenas and 7 enemies (not counting vehicles or popcorn flood). Each encounter can play out differently even if the arena, enemy placements and composition are the same (and even moreso when they ARE different). It's not ideal to reuse the same circular arena 40 times, but in a game with such varied outcomes it's not quite the end of the world. The core systems do a lot of the heavy lifting, which I might be biased toward given how interesting I find such things. As always in a shooter, aiming is going to be the key factor. If you noscope headshot an Elite, you can get away with otherwise boneheaded positioning choices. A player with great aim can go through with less solid plans, while missing a shot can force you to readjust your plan. If you take too long to shoot that Jackal, the Elite approaching from behind might make your life a lot harder. If you couldn't tell, positioning is quite important too, and arenas often spread cover far enough apart to where changing your position is not done easily. If a Random Enemy is Approaching, do you run away and risk taking more damage, or do you stay put and bet on your aim and dodging skills? (Notice how the RNG makes the game more dynamic by working in tandem with the skill checks). Do you run into a group of Grunts faithful that you can stunlock and punch all of them? Or do you let them live longer and possibly take unfavorable positions such as attacking from multiple angles, which makes dodging much harder. Aiming and shooting is a basic skill check with a very binary outcome (you hit 'em or you don't). It's exceedingly simple on its own, but when the game has so many variables that are always changing states, like those examples of both you and enemies' positionings, but also their current behaviors, ammo counts, your shield and theirs, weapons on hand and on the floor, etc. Each passed or failed test has a butterfly effect on the whole encounter and your own gameplan. RNG is also a simple way to achieve unpredictable results, but it too is complimented by these states (for example, that earlier Random Enemy Approaching situation will probably trigger a different response in you if you only have a quarter shield left as opposed to full). Overall, the core mechanics of Halo are quite-well considered, creating consistently deep combat!
The only thing Halo really does wrong on a foundational level is the healthbar. The regenerating health itself is good, mitigating the frustration of getting shot from offscreen but still punishing the possible bad positioning that lead to it, and encouraging COOL people to get good at dodging and aiming so they don't have to wait for their shields to come back all the time. The longer recharge and higher shields lead to prolonged consequences as well, where you might see guys coming on your radar and realize you'll have to fight them with less shield than you'd like. Since enemies in Halo can move behind you randomly and dodging every projectile just isn't feasible, it makes sense for the game to not give permanent consequences for getting hit. This is offset by the actual healthbar underneath, which does not make sense for the game and often leads to more waiting behind cover like a loser or restarting on the slightest mistake to avoid permanent damage. On its own it's not necessarily bad, but combined with the game's checkpoints it kinda (really fucking) sucks.
The checkpoints are also more than willing to put you in a section with red HP, emulating the worst of F5 to save anywhere systems. In old PC games, sometimes it's better to go back to the last encounter and do it better so you have a better chance in the current one, and here you don't even have the choice. The healthbar does offer connective tissue between encounters, but the two weapon limit and AMMO also do that in a much more interesting way that results from your choices, and not getting clipped by a couple of needles from behind.
That two weapon limit is great at coloring encounters differently as well, encouraging strategic decisions but never railroading to the point of turning encounters into puzzles and removing that sweet sweet depth. You could run through Assault on the Control Room with the Rocket and Sniper, even if it is a tactical decision so poor it would put Reach Brutes to shame. The game feels designed around the Plasma Pistol, with it being the most common and versatile. It works against all three enemy types, but the nuance is that you have to charge it to remove the shields. Since you give up the ability to remove even Grunts through kills or stun, it's risky! Of course you can do it from behind cover, but it's worth noting that the charge shot's chance of hitting drops off with range, especially in the more open arenas, and especially especially against Elites who just love to dodge the thing. Here we see that weapon effectiveness against enemies isn't always straightforward, affected by range and level design. You might be inclined to use a Plasma Rifle instead, which too murders Grunts and works well on Elites, but can be rather unreliable against Jackals unless you get close enough to circle the assholes.
The Magnum, the best gun ever, is often found accompanying its fellow pistol. On its own, it's far from the best against Elites and inconsistent against Jackals. Your go-to isn't a single weapon, but instead a combination, which you are given reasons to abandon. You could run low on ammo, you could find a power weapon, you could be playing a fuckin' flood level. Although it might seem better to have every weapon be the same level of viable, there's arguably something gained through not adhering to that. Power weapons like the Rocket and Sniper demonstrate this quite well, since their limited ammo means every use of them is high-cost and a big deal, and running out can lead to some great "aw shit" moments. The same can be said for something like the Needler, which generally sucks but can be used in a pinch. Killing a Grunt and taking it from him to stick an Elite as you cut off his cover routes is fun, the knowledge that its more situational and less generally reliable making those scrappy strategies more satisfying.
The Flood are quite stupid, both in their design and quite literally. Their straightforward behavior doesn't really lend itself to any of the strengths listed above. It makes sense why Flood wouldn't take cover or react to their fallen brethren in any way, but it still sucks. Making the Shotgun into their obvious go to isn't bad inherently, but unlike the plasma pistol it's actually the obvious best option on its own. Thinking about your secondary against the Flood is like thinking about what color underwear you're gonna put on. Since the enemies aren't particularly fun, trying to run a sub-optimal loadout against them would be a great way to make yourself hate reloading and slow movement speeds. They're also often paired with CE's worst level design sins: reused hallways that barely feature any interesting cover, usually one-way crevices which lead to hiding inside instead of gliding between. What about hallways as opposed to more circular or open arenas that give the player and enemies a more complex relationship with the environment? Stupid wave defense sections where enemies flood in from one choke point so you never have to think about anything too complex, everyone's favorite! They even hit you with the combo of locking you into these sections! Their more frantic, charge-heavy nature puts the player on the backfoot in the way the Covenant never did. They start off very stimulating and refreshing, but quickly give way to tedium. They’re too reactive, not proactive or tactical enough in a game that otherwise nails that balance. The focus on fast decisions over complex ones gives them very little longevity, and ultimately become far more exhausting than if there were just 5 more Covenant levels. On the bright side, once the other enemy types are reintroduced, encounters become good again, even introducing new strategies like waiting out the infighting and kiting enemies into certain areas to spark it.
Still, pacing is one of those aspects that defines the "game", the part built on top of the mechanics and systems and creates the holy holistic experience, the sum of the parts. The Library would be a great example of a colossal failure in this department, since it fails to distract from (and in fact takes 10 megaphones to tell you all about) the shallowness of the Flood. Common criticisms of Halo tend to be aimed at this experience, with many claiming the lack of visual variety just makes them not wanna play the thing. Can't say I blame anyone who got fatigued with the game, I used to feel the same way, but I just don't anymore. Of course better pacing would be appreciated (I often skip the Library now), but surely in a game whose foundation lends it such diverse, dynamic gameplay, it's not the most important thing. Of course I'm biased because the best parts of Halo 1 are the parts I find most interesting in 99% of games, because at some point you skip the cutscenes and stop seeing the game for how it looks.
Despite some clear missteps, Halo is a wonderful game. In a word it's dynamic. Let's take Hunters as a sort of counterexample. Most people don't think they're anything special since you can employ a pretty one-note strategy of baiting out an easy attack and shooting them from behind. This is lame because it's not really a decision, it's a formality. You've solved the Hunter problem, permanently. Thankfully the bulk of the game is not Hunter encounters. Halo rejects formalities for ever-changing scenarios, leading to consistently engaging, good-ass decision-making. If you imagine each encounter as a 30 second bubble that represents everything that could happen, that bubble is reeeeaaaaaaallllllllly big. Add up every complication that can happen in 30 seconds of Halo, and you get a game that’s fun for hundreds, maybe even thousands of hours. Player creativity can arise from mini-situations that the developers probably never saw coming themselves. You can't solve the game if it's creating new problems on the fly. The game creates a ton of complex situations to work through, and all out of mechanics that are intuitive and simple to parse (tech skill is awesome, but the game's situational depth proves its not necessary to be a sick game). The mechanical foundation is so robust that the developers managed to build the ugliest building on top of it, and it still works better than most games I've played.
Saying Halo 1 has a ton of variety probably sounds like a stretch to most, but don’t be fooled by the visually repetitive exterior (ironically more common in the game’s interior rooms). Firefights may not look different, but they play different. Enemy variety is often made out to be important for variety's sake, but Halo shows the truth in quality over quantity. Hell its biggest flaw is not sticking to that all the way. While there is value in the things Halo lacks (even I sometimes do the Banshee skip in Assault), it serves as proof that flash, polish, and high production values need not be the priority of video games. Halo more out of 3 good enemy types than most games can with 5x as many. Its limited content and surface variety is a footnote compared to what was achieved with its gameplay. It's a shining example of a game that's so varied and replayable not through content, but through the gameplay systems. Put simply, real ass video game.