definately xbox
xbox may not hav as many games, but the games that they do have are just amazing, and xbox live is amazing too (high-speed internet needed). i have an xbox and an advantage that it has over ps2 is that it has an internal memory so you dont have to waste money and have to deal w/ memory cards that just fill up too quick. with an xbox you can save your games with no problem.
i love my xbox, but ps2 is good too, but game cube, stay away from it, it has second rate games, have so many friends who have bought it and hated it and had to lose money because they traded it in for a ps2 or xbox.