That's damn near impossible, man. Wind Waker, Paper Mario: Thousand Year Door, Metroid Prime, and Pikmin 2 are all on my favorites list, probably even top ten. More incredible games on that system than I can count.
But if I had a gun to my head and had to pick one on sheer scope and the amazing feelings it left me with, I think I'd have to go with Wind Waker too. But only in the gun scenario! Otherwise it's pretty much impossible.
Currently playing:
Bloodbath Paddy Wagon Ultra 9