But that's just it. It *wont* do the same thing the consoles do. I play console games because I'm tired of monkeying with the PC. I use my PC for work, web, etc. I use my Xbox for games. Wanna play a game? Pop it in and play. No setup. No fuss. Just enjoy. There's also almost no possibility that the game will have difficulty with YOUR system. (The slight exceptions being poorly developed, quickly released games. This rarely happens with good titles, so it's really not a major consideration.)
And it'll be a good tilt more than $100 more to get a PC that'll do what an Xbox360 can do. To match the capabilities (graphically) of an Xbox360, right now, you'll need about a $600 machine (not including monitor, operating system). The xbox is $300.
I understand that that $600 machine can do more than play games, but for that extra flexibility, you'll also need to mess with it. Driver updates... windows updates... anti-virus... anti-spyware... blah blah blah. Oh, and don't forget the installs... How I loathe the installs...
I use Linux as my PC, so I avoid most of the cruft of computing, but Linux, sadly, just doesn't cut the mustard for gaming. Thus, I game with consoles.