xbox owns online

and now has plenty of quality games.
ps2 owns square enix

and has a billion game choices (lots of rpgs) + ps1 games, but it doesn't look as nice, and the online stuff isn't nearly as killer... x-box live is really the way to go if you're buying for online gaming.
if you don't know about live, it has instant messaging built in, and you can ask people playing OTHER games if they want to switch discs to play you... much easier to keep track of good friends/gamers, don't know about the cost though... when it came out (forever ago) it was something like 50$ for a full year, but that was before it became really big.