I'm generally more of a Sonic guy, but Super Mario World is one of my favorite platformers. As for being the greatest game of all time? Well, maybe not
the greatest IMO, although it's definitely high up there.
It
is my favorite Mario game of all time, except for Mario 3 possibly. In terms of that, I think James Rolfe put it best: whether SMB3 or SMW is the better game depends on
what you're in the mood to play right now. Today, I'm in the mood to Super Mario World, but for all I know, a week from now, I'd rather play Super Mario Bros. 3