Why use consoles? They're cheaper. They're more social. XBox Live is killer. You can play them more comfortably. Controllers are far more natural for gaming than keyboard/mouse, and comfortable in the hand.
PC gaming is good. But I much prefer console gaming. I suppose if I wanted to I could hook my PC up to my TV, and hookup a wireless controller to the PC as well and have the same experience. But, I wouldnt' have Live, and play with multiple friends would be
If that ever happens, I'd happily ditch consoles. But I haven't in nearly 20 years, because the experience is totally different.
And, for the record, most console launches outperform the PC hardware of the day. Typically for about a year.
This generation may lengthen that time, because of the new architectures. But, it's hard to say right now.
Back to the original post, though, I'm disappointed in the 360 lineup. I'll be getting one at launch, because the controllers are far more comfortable, but the first round of games isn't that impressive.
I'm sure in 3-6 months it will be, though. By the time Sony's console comes out, there are meant to be more than 100 Xbox 360 games on shelves.