It might be possible to buy two systems at a pawn shop for cheaper than a new one. Just make sure they gives you a couple days warranty so you can make sure they work
Let's compare Exclusive titles.
Gamecube: Metriod Prime, Zelda Windwaker, Tales of Symphonia, Metal Gear Twin snakes, Resident Evil 0, Super Smash Bro melee, Mario Kart
Upcoming GC exclusives: Resident Evil 4, Metroid Prime 2, Baten Kaitos Metal Gear Solid 3 New Zelda...
Xbox: Halo, Ninja Gaiden, Knights of the Old Republic, Morrowind
Upcoming Xbox exclusives: Halo 2, Doom3, Fable, Knights of the Old Republic 2, Jade Empire...
Playstation: StarOcean, Final Fantasy X, XenoSaga, Kingdom Hearts, Gran Turismo 3, Jak and Daxter 1 & 2, Rachet and Clank 1 & 2, ICO, Onimusha 1-3, WWE Smackdown series, ATV Offroad Fury and many other great ATV and Dirtbike games, Soul Reaver 2, and it plays every PS1 game...
Upcoming PS2 exclusives: Gran Turismo 4, Final Fantasy 12, Kingdom Hearts 2, Rachet and Clank 3, That's about it... Grand Theft Auto: San Andreas will be out on PS2 first but it's not totally exclusive.
Non Exclusive games include: Splinter cell1 & 2, Spiderman 2, Tony Hawk Underground, Need for Speed Undergound, Silent Hill 4, Prince of Persia, Grand Theft Auto(PS2 and Xbox) and more.
Most(ok EVERY) Non exclusive games look better(alot) on the Xbox. I personally like PS2 because of the overall selection of games and if you're willing to go back and play games from Sony's endless library then you may enjoy it more, but if you only plan on picking up recent releases and upcoming releases I'd say get an Xbox. The gamecube only has a few games but they are all excellent, It's hard to pass them up, plus you can pick up a gameboy player and play Gameboy advance games like Final Fantasy Tatics advance, Golden sun 1 & 2, all the classic mario games and more.
I hope this helped. I've always been a PS2 fan and It pains me to recommend an Xbox over it.
*edit: I know a few games I listed are also PC titles, but let's just pretend they're exclusive ok...