I am a XBox owner and definitely plan on getting the 360 for a lot of the reasons everyoen described above. In terms of V's point here, the original XBox was a little too light on RPGs (although it did have KOTOR, Morrowind, Fable). Fortunately, the group that developed Final Fantasy was hired away to do some exclusive XBox stuff and the new Elder Scrolls: Oblivion will be 360 only (with some of the most amazing in-game graphics I have seen to date).
More than anything else, both systems will be pretty kick ass and the key will be whether people will design great games for them or not. Personally, I worry that there will be too much focus on making things look amazing to the detriment of gameplay and... God forbid... fun.