What I find funny about this thread, is that hardly no one is mentioning the PS2 as an overhyped system. IMO, it is. Yes, there are some really great games that it exclusively has (DMC being my fav), but this year, it's fallen flat on it's face compared to XB exclusives. Same for GC (of which MP2 will be the only game I buy for it this year).
For all the "Why would I need an XB, blah blah blah" speeches, I honestly think the same goes for the PS2, unless you just happen to have a hard-on for Japanese RPG's.
As for whether or not people will pick up an XB for Fable? Some will, but I agree with most here that Halo 2 has much more drawing power. Personally, if I didn't own an XB, I'd have to say that getting one now would be very temptin. Not only for Halo 2, as well as Fable (which I think will have as 2 of the best games this year), but also for Crusaders: Kingdom Under Fire, Otogi 2, KotoR 2, Jade Empire, and Mech Assault 2. Then of course there's also Doom 3, and SC:Chaos Theory for those of us too poor to afford upgrading our computers (or own a Mac).
Added to that of course are the older (not to mention, absolutely kick ass) titles, that can be bought for next to nothing now, like Panzer Dragoon Orta, Ninja Gaiden, Otogi 1, Crimson Skies, Halo, and Riddick.
If one still wants to claim that theXB has nothing to offer, that's fine, but I honestly feel the same for the PS2 (MGS3 is all I can about on this system. GTA:SA I could care less about) and the GC (MP2, RE4, and the next Zelda), except for a few select titles.