I've got to be honest:
Whenever I look at the PS3's or 360's library, I see "FPS, FPS, FPS announced, FPS, racer, Sandbox game..." to the point that It becomes redundant to me. Not that I don't like FPS', but such a steady diet of them is wearing thin for me. I don't particularly care for the 360's online capabilities as I only play online with a handful of Games (Madden, the odd racing title) and while the 360 does have compelling games, the library doesn't seem diverse to me at all.
I realize that this ISN'T the case with a lot of other people, and that's cool. But I can't help but notice that a good many of the games that GAF is anticipating on the HD consoles are FPS', and I just plain don't like that genre enough to pick up a system for it right now.
MS is doing some fantastic things with the 360 (finally) and they're realizing that diversity is the key to success rather than appealing to the "mature" market, Bioshock looks fantastic, I've wanted Gears for a while, and Mass Effect may tip the scales to get me to buy one eventually, but for the most part, I much prefer what the Wii is offering or set to offer in comparison.