This is the funnest fighting game ever!
Even though it is very similar to the original, Street Fighter II has better new moves, characters, stages, etc. Overall, it's just a much better game than the original.
Of the Super Nintendo and Arcade versions, I prefer using the SNES controller, but both versions are about equally fun. Some combos are easier to pull of at the arcade, but I also like having Street Fighter II available to play at my house.
The graphics are improved, they are still cartoon so don't expect any 3D effects. For a 2D fighting game, SFII looks fantastic and the character models are even better, they look great on Super Nintendo! Of the two versions, well three counting Champion Edition on Genesis, the arcade version looks about the same, probably exactly the same as the other versions but it looks a touch better than the Sega Genesis edition.
The sound is great. The character have there own unique, well battle cries or grutns or whatever you want to call them and the music is fast, catchy, and nearly flawless.
The fun and fast fighting will last you a long time. You will especially love the great multiplayer and I assure you that you will be playing the multiplayer for a long time.
Right now the game Used only is $7.99 which is definitely worth it, so I suggest you go buy it now if your one of those who hasn't.