GTAIII does not make or break a system. There's a lot of multiplatform games, and very few exclude the GC. Just look at big selling titles like the new Tomb Raider game, which is available for every console under the sun. The Tony Hawk series is another big seller, and I specifically bought that for my Gamecube since the graphics were a notch better. Then you have exclusive titles like the Resident Evil remake, Super Smash Bros. Melee, Donkey Kong's Jungle Beat (you really can't deny the genius of this game), Fire Emblem, and Eternal Darkness. You also have titles which start out as exclusive and only move on to other consoles after selling a bajillion copies like Viewtiful Joe and Resident Evil 4. The Gamecube definitely has a lot more going for it than its first party games, though those alone make a good justification for buying the system.