The black sheep of the Mario series, due to how different it is and the fact that it's technically not even a Mario game. That being said, I still really liked it. The controls do take a bit to get used to, but once you do there are really good and responsive for the time. Picking up and throwing enemies is a fun gimmick that this game introduces, as it creates more strategy when it comes to beating them and combo-ing a bunch of enemies in a single throw. The level design is incredible for the time and manages to be both difficult and fair (For the most part. A couple later levels like 6-2 have BS trial-and-error moments, but these are few and far between). The soundtrack is pretty good, though there are only about 7 tracks in the game. The bosses, while primitive today, were probably revolutionary for the time and they all put up a pretty good fight, even Birdo, this dinosaur-looking miniboss you fight at the end of each level. And lastly, I do like how each playable character has different stats to make them feel different from each other and give them special advantages/disadvantages.
No game is without issues, though, and I do have a few issues, some of which really detriment the game for me. Firstly, and this is probably the biggest issue, the lives system sucks. You get most of them by cashing the coins that you collected in the levels' subspace areas in a slot machine that shows up at the end of every level, and by a match of 3 or a correct sequence of images on the slot machine, you can get-5 (1-10 in the SNES port) extra lives. Now, this isn't a bad concept and could be really fun, but it's held back due to the fact that the images on the slot machine scroll way too fast, and it's hard to differentiate the images at such high speeds due to the fact that a lot of the images share color schemes with another image, making them all blur together. As such, you'll frequently only get a small handful of lives by the end of the minigame, and as the levels become harder and longer, your lives will dwindle much quicker, making the game much more frustrating and stressful. I mean, sure, you could find 1-Ups in the normal levels, but those are incredibly rare and a couple of them are even RNG-dependent. I have other minor issues with the game, namely how Peach and Toad are noticeably more OP than Mario and Luigi, the quicksand is way too strong and is pretty much an insta-kill if you wandered into it while carrying something, crouching is useless due to the fact that your crouching hitbox is still pretty massive, the enemies respawning can be super annoying at times, and the Super Star is basically useless due to the fact it has a way shorter duration compared to SMB1 and the Lost Levels, but those don't really hinder my experience unlike the lives system.
If you can get past the flawed lives system or feel like spamming savestates to compensate for it, I'd strongly recommend SMB2. It's not my favorite Mario game of all time, but it's still a really fun time and a massive step-up from SMB1 and the Lost Levels.
No game is without issues, though, and I do have a few issues, some of which really detriment the game for me. Firstly, and this is probably the biggest issue, the lives system sucks. You get most of them by cashing the coins that you collected in the levels' subspace areas in a slot machine that shows up at the end of every level, and by a match of 3 or a correct sequence of images on the slot machine, you can get-5 (1-10 in the SNES port) extra lives. Now, this isn't a bad concept and could be really fun, but it's held back due to the fact that the images on the slot machine scroll way too fast, and it's hard to differentiate the images at such high speeds due to the fact that a lot of the images share color schemes with another image, making them all blur together. As such, you'll frequently only get a small handful of lives by the end of the minigame, and as the levels become harder and longer, your lives will dwindle much quicker, making the game much more frustrating and stressful. I mean, sure, you could find 1-Ups in the normal levels, but those are incredibly rare and a couple of them are even RNG-dependent. I have other minor issues with the game, namely how Peach and Toad are noticeably more OP than Mario and Luigi, the quicksand is way too strong and is pretty much an insta-kill if you wandered into it while carrying something, crouching is useless due to the fact that your crouching hitbox is still pretty massive, the enemies respawning can be super annoying at times, and the Super Star is basically useless due to the fact it has a way shorter duration compared to SMB1 and the Lost Levels, but those don't really hinder my experience unlike the lives system.
If you can get past the flawed lives system or feel like spamming savestates to compensate for it, I'd strongly recommend SMB2. It's not my favorite Mario game of all time, but it's still a really fun time and a massive step-up from SMB1 and the Lost Levels.