If a game retains everything that made it great after fifteen years, then it truly is a success.
When I was 11 (I'm 26 now), there was nothing more desirable than owning a Super Nintendo and this game. I was in my local mall, playing arcade games which were technically superior than any home console (save Neo Geo), when my brother and I walked next door to Electronic's Boutique (anyone remember those stores?). And there it was. The Super Nintendo with a fully-playable copy of SM World. I was instantly taken in, and amazed by what I saw. After getting a chance to play for myself, I was convinced that home consoles were going to make the arcades obsolete.
Of coarse we couldn't afford a Snes, so my brother and I would always hang out with the neighborhood kid who was fortunate enough to have one. Soon enough though, my brother got a Snes for his birthday, and we were in heaven.
It's strange, how the first game available for the Snes wound up becoming the definitive title throughout it's glorious lifespan. Super Mario World was, without a doubt, one of the greatest games ever made, and it still shows when you play it today.
If you have an actual Snes, get this game, if you haven't already. If you own a GBA, get Super Mario Advance 2: Super Mario World right now. If you own a Wii, download this VC game without thinking. If you don't own any of the above systems, find a friend who does, and play Super Mario World. You owe it to yourself to find out what video games can be; fun and memorable, which is what any developer could hope for.