Never been too big on most of the 2D titles, ironically enough. Yoshi's Island is one of my favorites too, as are Galaxy 2 and the original Paper Mario.
if i had a top 5 it'd probably be something like:
1. mario & luigi: bowser's inside story
2. mario kart wii
3. super mario 64
4. mario & luigi: superstar saga
5. wario land 4 if that counts as a mario game