Prince of Persia is on Gamecube, and GTA is on x-box, so those aren't exclusives. And PS2 definitely has the largest library of games out of the three--the library just doesn't include a great deal of what I like. If you like RPGs and sports games, though, it's probably the sytem of choice.
But I should probably mention, I play PC games more than any of the console systems. Warcraft 3 and Wolfenstien have had me hooked since the beginning of the year. But like I said, I'm a multiplayer nut.