Ive got both XBox and PS2.
Although decent new games for both are pretty thin at the moment, the PS2 has a decent selection released over the last 12months or so.
Xbox has Halo and thats about it.
There is some promising games for both consoles released soon, so it may be a good idea to check those out to see how many of those interest you. (try www.gamespot.com
for up to date info)
Im looking forward to Sega GT2002 (Xbox), its looking like it may finally knock Gran Turismo off its perch.
(though they did say that about Gotham racing - Lame)
But if I had to choose one or the other, go the PS2, but in 6-12months it may be a different decision....