Hokay now...
Sonic Adventure 2: Battle (Absolute poetry and the game for which I bought the system, really)
Sonic Adventure: DX
Sonic Gems Collection (If you like retro)
Sonic Mega Collection (If you like retro)
Sonic Heroes
Metal Gear Solid: Twin Snakes (Ah-Meh-Zing remake. And I mean remake, not a lousy port with barely any improvements)
Resident Evil RE-Make (Same)
Resident Evil 0
Resident Evil 4
Luigi's Mansion
Bloody Roar (Damn, I love that fighting game!)
Time Splitters 2 (Woot!)
Shadow the Hedgehog (My acquired taste, but I like this game, so you might too)
Metroid Prime 1 and 2
Super Smash Bros. (First game I've ever played in the series and deffo my favourite)
Tony Hawk Pro Skater games (They're all quite cool)
Sonic Riders (Say what you will, I LOVE this game on the Gamecube pad - fluent racing, cool tricks, real damn fast action)