I'll probably end up getting all of them. Here's what I think:
Xbox 360: So far, I'm reasonably impressed. The games look good, even though they're only at 33% of the power of the system at this point, so they'll look better come launch time. I'll end up getting Xbox Live with this, I'm sure, and we can all play Halo 3 together. I don't know about the whole selective-backward-compatability, though.
PS3: Enough's been said about the shitty controller, so I won't go there. Most of the footage shown so far hasn't been done in real-time, and Sony is probably bullshitting about the power of the system. Nevertheless, I will end up getting one for Final Fantasy, MGS4, and hopefully Ace Combat 6. Plus it's backwards compatible, which is a plus.
Revolution: Not much has been said about it, though I'll get one. I can still play my Gamecube games on it, and I'm sure Nintendo will come up with some good shit for it.
I'd say I prefer the Xbox 360 at this point, though my excitement for each one of them continuously fluctuates.