My favorite was The legend of Zelda The Widwaker! It was such a fun game, I completed every side quest and I LOVED THE GRAPHICS!

My Second favorite was The Legend of Zelda the 4 swords, 3rd Luigi's Mansion, 4th Sonic Heros, 5th I think it was Mario Soccer or something,6th Another Sonic Game I can't remember the title,

What about you?

Soul Calibur 3 (or 2? I don't remember) Because it was the only game that I played in the GC =P

Pikmin! Of course....

Wind Waker, Super Smash and Mario Sunshine

1 - Zelda Wind Waker
2- Viewtiful Joe 1
3- Eternal Darkness
4- Turok (multiplayer)
5 - Tales of Symphonia

Tales of Symphonia
Baten Kaitos 1 & 2
Paper Mario: TYD
Pikmin 1 & 2
Sonic Adventure 1, 2 & heroes
Wind Waker

Paper Mario: Thousand Year Door was probably my favourite. I've bought it 3 separate times to replay it. I always tell myself I'm done with it, but then I get that urge.....

Pikmin(1&2), Resident Evil (0&1), Wind Waker, Mario Sunshine, Metroid Prime 1&2, Tales of Symphonia, Sonic Adventure 2 Battle

RE remake, Metroid Prime 1+2, Pikmin 2, Viewtiful Joe...sigh, even though noone bought the damned thing it was a damn fine machine.

Everyone says these or most of these at some point.

Super Smash Bros. Melee
Mario Sunshine
Metroid Prime 1 & 2
Wind Waker
Eternal Darkness
Animal Crossing
Pikmin 1 & 2
Resident Evil 4
Soul Calibur 2
Prince of Persia: Sands of Time
F-Zero GX
Twilight Princess
Rogue Squadron 2 & 3
Final Fantasy: Crystal Chronicles
Tales of Symphonia
Killer 7
Naruto: Clash of Ninja
Viewtiful Joe

Some personal favorites of mine, some flaws that prevent them from reaching greatness though.

Pokémon Colloseum/XD: Gale of Darkness
Kirby Air Ride
Double Dash
Wario World
Sonic Adventure 2: Battle
Billy Hatcher and the Giant Egg