NFS Underground is a blueprint for it's sequel and the single most important game in the series, which set the direction the series would mostly be going in for the next 20 years.
However, on it's own this game is broken, repetitive slog, which forces the player through repeating tracks over and over again while also having the opponents cheat their way to victory no matter what difficulty you pick. Each of the player's wins feels like luck since most of the time the reason why it happened is because the rubberbanding AI wasn't as broken as it usually is, the game's hyper realistic collision physics haven't flipped his car over on a straight road for no reason, or the traffic car hasn't spawned right behind a blind turn, sending the player's riced Honda Civic spinning 360 degrees and flying 3 meters into the air.
Do I recommend playing this game? Eh, purely for historic value. It looks really good for the time, the car selection is overall solid, and the modding options can look cool.
The music also has a silly childish charm to it, looking at it in the retrospect. Since it usually forces itself to be cool so hard that it turnes to being cringey, which in itself provides unintentional comedic value, making it great, albeit again not in a way it was originally intended.

I was very surprised by the amount of times the n-word was said in this game's unedited soundtrack when I looked up the uncensored version

AMAZING chases, meh the rest of the game

The best thing about this game is that Battle Royale mod exists because of it

It's the first Berserk game to be released, and honestly, despite being the only one to have an original story, it's bad.
The gameplay consists of "run to the end of the hallway, see if the door lets you finish the level. if you end up running into an open door with nothing happening, slaughter everything alive, then proceed again. fight a boss maybe. repeat until end credits". That is also paired with the combat where your huge sword hits every wall (which while is pretty obvious to why doesn't nake it a good design choice) until you fill your DT and it doesn't. The items also never felt like being of any use, you will only be healing yourself with elf powder to tank more hits, the rest were pretty much pointless.
The story itself felt like it's just one exposition dump paired with the devs going "oh, remember this thing from the manga? we have it here!". Because of this it never truly offers anything new and unique to the world, the whole conflict and themes are essentially Lost Children arc, minus the bug loli. Zodd appears out of nowhere just to remind everyone that he exists and to have one fight without bringing anything of value to the narrative, the behelit is pulled out of the ass at the last moment just to have yet another underwhelming boss fight. And the cover art girl is here to do nothing and gasp at the ongoing events.
The only good thing here is the soundtrack, and the fact that thanks to the fan retranslation I didn't need to sit through the horrible English dub.

nice assets and general art direction, terrible level design. who the hell though that open areas with no cover is a good idea for an HL mod?

I'm just gonna say... Sabato Nabe is the best singular fandisk ever released

Adrian Shephard makes a pretty funny face on the cover art NGL

oh and the games is good feels like a natural expansion of HL1

A bite-sized HL1 expansion you can beat in a sinlge sitting, despite coming out later it uses no assets from Opposing Force. Nothing wrong with it, but it's not particularly outstanding or memorable either.

Ah yes, challenge. Didn't know it meant getting killed by a thing you couldn't predict coming, loading a save, avoiding the said thing, only to die again from another unpredictable thing, repeating the process. Such game design, such mapping prowess!
But seriously, I have no clue how this was allowed on Steam. There is not a single good thing about this mod, it looks and plays like ass, even it's idea of texture work is taking existing HL textures and drawing with MSPaint on top of them.
Oh, and the title is literal clickbait. No, it's not related to Quake in any way other than GoldSrc engine, it's named like that to confuse you that it is.

A short (~20 minutes long) technology demonstrator game released to showcase new (at the time) features in the Source engine. Also includes a test for the developer commentary system which was so well recieved, that it appeared in nearly every Valve game going forward. Too bad they only came up with it now, I wish I could see this in HL2 itself.

At the time, Valve seriously considered releasing half-life content regularly in episodic format. Because of that, they allowed themselves to release this, which essentially setup for what's coming next (spoiler: what was coming was ep2 and nothing else), so there is really nothing outstanding about this game in isolation. Of course, it wasn't meant to be experienced in isloation, and should not be rated this way.
Nothing wrong as far as gameplay goes.

A short good to mid mod for HL2 where you play as a metrocop shortly prior to HL2's events.
The opening sections and the rebel camp raid were fantastic, by the end of the game it starts dragging on with long underground sections, ending in a poorly designed bossfight where you don't know if you're winning until it ends.
Really, the only major reason you should be playing through this is the sequel.

Imagine Hunt Down the Freeman, but actually good.
This is probably the besat HL2 mod out there, boasting it's great level design and variety, well written story, charismatic characters, and improvements to base HL2 formula, and all this while being as lore friendly as possible for such an ambitious project.
You play as Bad Cop/3650's clone afyer the events of EZ1 who is tasked by the Combine to search and capture Judith Mossman, while being granted freedom of thought just for this mission, which separates the MC from all the other Combine soldiers. Which means, he can talk. Which in itself means, that now we're playing as a Build Engine era protagonist, but this time in HL2 setting.
Surprisingly enough, the idea actually works, because the 3650 is extremely fun to listen to and play as. A lot of character has been put in all of his interactions, as well as weapon animations. The story brings in a lot of unique twists which I won't spoil. I will only say that it is truly a by fans for fans project, which means it's highly recommended to play thorugh at least HL1 with all the expansions, HL2 with both episodes, and at least Portal 1 prior to going into EZ2. And also, make sure to bring Wilson along with you :)
As far as gameplay goes, it seems the devs were playing through HL2 and were taking notes about everything they didn't like, because basiclly all of mine personal issues with it are fixed here. A lot of surprises with returning foes happen, as well as brought back remotely activating explosives from HL1. The expansions are so big that calling this mod Half-Life 2: Opposing Force doesn't feel like stretch at all.
And what's the most baffling about this project is that it's absolutely FREE.
TL;DR It's good, please play it.