Actually, without any isult meant, I'd like to add a slightly less biased view.
The xbox, despite it's microsoft ownership, is actually a very good product. Yes, HALO was the flagship game for it when it was released, but since then there have been many great titles come out. Project Gotham Racing was one of the first racing games, and is quite entertaining, and over time more and more games will become available to XBOX owners. But for me, it's the little things that make it presently a better buy.
You can save games without needing to buy endless memory cards, and listen to music of YOUR choice in most games, from the Hard Drive.
The controller, while almost certainly copied from previous console controller designs, is much easier to use than that of the PS2. And if you don't like the size, get a Controller-S, which is simmilar to the smaller sized controller introduced in Japan..
Multiplayer play with more than one XBOX is SWEET. Get a switch/hub, get 3 mate's with XBOXes, some cheap CAT5 cables, 4 copies of HALO (over here its only recently you could even buy an xbox without halo) and you have an instant evening/day/night/weekend/month of fun.
I dont know how many of Tom Clancy's games are available on PS2, but the shear difference in release/development times means the XBOX has the upper-hand as far as hardware goes, and GhostRecon/Splinter Cell are a joy just to watch. As with Windows/Mac i don't think its a case of "is that game available" any more with consoles ( except with maybe some very obscure games) it's more a case of, what your friends have (seems to influence buying a lot), what has the best graphics/sound/etc, and what you can get the best deal on..