YI is my personal GOAT. It's the missing link between SMW and SM64. You have crisp, rewarding platforming, crossed with wide-open areas for you to dig into. It's got all of the classic, charming Mario imagery, but it's so much more lively than either of the two above. Enemies are expressive, animated, and hugely varied (I believe at one point I counted over 100 distinct enemy sprites, and even some of the recolors have drastically different behaviors). Yoshi is so versatile, and you can transition from one action to the next so smoothly. There's so much crazy experimentation you can do with this game (like it's often faster/more direct to spit enemies than egg them, and different enemies have a bunch of different trajectories/reactions to getting spat).
I certainly don't mind all of the collecting, because the game has a ton of cool secrets and one-off areas/enemies, and I love just poking around even without having things to go after. And while it takes its time to ramp up, there's some immensely satisfying platforming in there (and again, Yoshi just moves so well that even the easier stuff is pleasant). The levels certainly get long, but there's no timer and generous health/checkpoints. I'll just turn it on, play a stage or two, and it's a good time. Each stage is so fleshed out and has its own identity and little secrets (what's crazy is on top of all the collecting, there are a ton of SMB3-style secret areas that don't figure into 100% at all). I know that some people get fatigued, but in a game like this with so many natural breaking points, and with each stage being so rich and satisfying, I'd take two more worlds of this caliber of content.
In the ideal world, it'd be great if you didn't have to collect everything in one pass for it to count. And the GBA version is nice because it gives you a 100-point margin of error for each world (so in both games, you unlock an extra stage in each world by getting 800 points in that world. But the GBA version has a new stage in each world unlocked just for beating it. So there, you need 800/900 to unlock the old bonus worlds, while on the SNES you need 800/800). The GBA's exclusive levels are also really creative and well thought out. But man, the audiovisual downgrade on the GBA is unavoidable...if only there was a version with its content and the SNES graphics and music.
I think it's notable that the game has some generous workarounds for the collecting. There's the magnifying glass item that reveals all red coins, and a ton of items that let you get stars (which almost every stage will give you more than enough of anyway, and always provides them in groups), particularly the +20 star item that essentially lets you ignore that category. And you can unlock the ability to play bonuses for items infinitely. Or, as folks have said, you can just savor the beautiful world and the non-essential secrets and ignore 100%. There's something for everyone!
(I know, there are legitimate reasons not everyone flocks to this game. But I wanted to inject some positivity toward it in this thread).
Anyway, just out of curiosity, I checked my SNES Classic, and I have put about 8 hours total into YI. Now, my first child was born a few months after I got the SNES Classic, or that number would have been much higher. And that doesn't account for my Wii U VC version, my GBA cart, or my SNES cart, all of which have seen me 100% it multiple times. Or the *ahem* method through which I recorded my LP of it. What I'm saying is I've probably surpassed 76 hours of YI in my life, but doing so since the SNES Classic debuted is quite impressive.