Man, this game holds up well!
I recently decided to play through Super Mario World again and I must say: This still is a great game!
The gameplay for example: The jumping still feels great and the flying with the cape never gets old. To differ from the earlier games in the franchise, they decided to add in Yoshi, who can stomp and swallow certain enemies. This adds another extra layer of depth to the game, that just keeps you interested and offers extra solutions to the (simple) problems you face in the game.
The enemies vary from Koopa's (The dudes with the shields) to Ghosts (You know, Ghosts) and even Dinosaurs and Moles! The bosses are pretty easy to figure out, although you will fail some of them on the first time you try to beat them. The final boss encounter, with Bowser ofcourse is pretty much the hardest time you'll get within this game, mainly because when you fail, you have to fight your way through his castle all over again. Luckily you have different routes you can take to get to him.
When you are done, there are soo many more secrets to be discovered, such as extra levels and hidden paths on your way to bowser.
I still had a ton of fun with Super Mario World again, even after the 17 (!) it has been since this game came out!
If you can't get hold of the SNES version, you should definately try to get your hands on the Virtual Console version or the GBA game that goes under the name of Super Mario 2 GBA.