apart from whatever has been said , ... xbox is my first choice , if only because with a little modification you can use it to store games , play games (duh) , play avis mpeg mp3 ... surf the net ... use it as a print server ...

PS2 has Kingdom Hearts and Final Fantasy though, and easier to put into the car.

So ...
if you want RPG games and button mashers , get PS2
if you want a media centre , future upgradeability , portable games , and FPS ... xbox is your console.