ive used both (ps2 and xbox)
the ps2 is good (theres a ps3 in the works) and have a large selection of games
xbox is basically a computer, so you wont need to buy memory cards. also you can download music onto your xbox to have playing while you play games. xbox has a lot of games just like ps2, but it has a monoply on halo (one of the best selling games ever)
i also play pc games
imo game systems are good for sport games and action, shooting games
pcs are better suited for strategy games.
hth