Super Mario World, though its caked with nostalgia for me so I haven't played it in ages.
The answer that will get me shot? Paper Mario Sticker Star on 3DS. I just found it absolutely charming, from the music to the visuals to the humor. I have still yet to play TTYD which I've heard is a masterpiece, so I came into Sticker Star blind to the Paper Mario franchise.
Damn you and your thoughtfully written nuance!