It's a bit of nostalgia, personal preference, and just overall masterful developers - but Super Mario World is a solid 10/10, easily the best game I've ever played. SMB3 is excellent as well.

For me, they still stand the test of time. I was a huge Sega fanboy back then, but I also loved Nintendo and the games they had. SMW just always blew me away, so every time I play it I think of that time. How advanced it was, how it played so much better than anything I've previously played. It was a serious masterpiece, and IMO still is.

Definitely a must play. Depending on your age, though, it may seem not as great as I'm claiming. I think it still is, but that's from my point of view. I'd really be interested in younger people's opinion that grew up on the Gamecube, Wii, and later console versions of Mario.

Like @R5N said - a lot of staple design concepts were pioneered in those games. Some that now are very commonplace. That's where I'm curious... Is it just normal for some while for us that played them on release they were so perfect and new?