I've got a PS2 and a GC (along with a few old school systems, a GBASP, and a DC), but I've really been wanting an XB lately.
I know it sounds pathetic, but as a married old fart (actually I'm only 27...), I find that I really don't have that many buddies coming by the house to play multiplayers these days. So, online gaming has become the only way i get to play against other real people, and the PS2 really just doesn't have the online coolness that XB has. I've been rockin both SOCOMs for a while now, and i'd really enjoy being able to play more similar games that support ingame chat.
Plus, i really don't get into most RPGs, and it seems like most PS2 online games are heading in that direction (except for the EA sports titles).
Oh, well... maybe with the recent price drop i will finally take the plunge....