Tonight I JUST finished Yoshi's Island, basically from scratch after losing a save. I have mixed feelings on this game now. I mean, it's a good well designed platformer, and the art style is pretty adorable. But I did not find it anywhere NEAR as a good as Super Mario World, which remains my second favorite SNES game after EarthBound. I have five major things I did not like as I was playing through/finishing it, so here they are. These are based entirely on my experience.
One, the power ups that existed were not used enough. You got them in 1-2 levels in each world, max, and they functioned only for specific purposes, in specific sections, in a way very different from SMW. I felt like far more could've been done with this and the way they were used felt a bit lazy compared to SMW and older Mario titles.
Two, the Yoshis were all the same. One thing I love in SMW is that the different colored Yoshis have different characteristics. The fact that this game featured Yoshi but did NOT do this felt like a real step backward.
Three, the controls. The controls were not as responsive or smooth as SMW. The downward smash and flutter jump in particular were extremely finicky to pull off. Maybe there was some timing to it I was missing, but for the most part, it felt like I pulled off these moves sometimes and not others basically at the game's whim. After taking a break from the game for a couple weeks after losing a save, I played it in my SupaBoy and noted the unresponsiveness. Thought there was a problem with the SupaBoy. But when I plugged it into my actual SNES, I had the same problems with the controls.
Four, the difficulty curve. I like games that get progressively more difficult from start to finish. But this game has a very sudden spike in difficulty. Now, it is during the last world, so I can sort of understand, but for the most part I was sailing through right up until world 6 when it went from fun and fair to frustrating.
Five, the final boss. For the first stage, see criticism number 4, as you have to use the downward stomp. The second stage is kind of cool. But when it comes to actually throwing eggs at Baby Bowser's face, it feels completely random whether they will actually hit or not. The targeting reticule becomes mostly useless and the range of altitude of your throw in which you actually hit him is ridiculously narrow. Plus, you can no longer throw eggs to retrieve Baby Mario should he be hit off Yoshi's back (which will probably happen), so you have to jump close enough to at least use Yoshi's tongue.
Now, don't get me wrong. It's still a good game, to be sure, and I'd say it's definitely worth playing. It just pales horribly next to its predecessor.