No respectful person on a computer hardware forum should even speak of playing FPS games on a console. Thumbsticks are the devil for free aim, but that's been argued ad nauseum in many an arena, so I'll move on.
Anyway, I'll get Xbox 360 when it launches, most likely. I like that they've reached out and scored some good Japanese developers (mostly those who do RPGs, a genre in which the Xbox had almost no titles) Eventually, I'll get PS3. My loyalties lie with Sony and they've had the upper hand because of software. Killer apps define the system, not the hardware, and the limitation of DVD9 on Xbox 360 kind of worries me.
Also, PS3 is looking at a constant price model. Instead of starting out at $450 and decreasing as the years go on, Sony is talking about a $300 price tag for many years. This will do well not to shun early adopters (I didn't grab PS2 or Xbox within their first year of release, but did so in subsequent years and saved nearly $300).
$300 for a machine with Blu-Ray? Sign me up. Of course, this could be a pipe dream and Sony may back out, but a great dream it is.