Zelda: Wind Waker
Zelda: Four Swords
Metroid Prime
Metroid Prime 2
Metal Gear Solid: Twin Snakes
Resident Evil 4
Super Mario Sunshine
Pikmin
etc..

I've had way more fun playing the games that I own on the Gamecube than any I've played on PS2 and Xbox (except maybe GTA:SA).
And I'm not a Nintendo fanboy (even though everyone seems to think so, just because I disagree with them), I'll be the first to admit that the PS1 owned the N64's ass. but, IMHO, the GCN is a great console with enough great games to justify my purchase of it. I can't say the same about the PS2.