Super Mario World and Super Mario World 2: Yoshi's Island are the best Mario games.
Yoshi's Island is an amazing game. The graphics, music, characters, everything is superb.
When I was a kid playing this on the SNES, I could appreciate the graphics and the music, but the gameplay involving baby Mario turned me off. His cries were just too annoying for me at the time. But years later I revisited this title, and loved it fully. No game to this date has looked this pretty, and it has some unique gameplay quirks going too. Even the story and the characters are great. That Kamek wizard dude was sweet, and all the boss fights are fun too. The last boss fight is one of the coolest boss fights in a Mario game.
Then Kirby just straight jacked this game's style in recent years. And as cool as it looked, I thought that game was super boring to play through. A little bit too easy difficulty-wise I guess?