Coming from a hardcore PC gamer from the mid-80's to the late-90's, I've switched to a 360. It was simply becoming too much of a headache to keep up hardware-wise on the PC side. It's definitely more expensive. On top of that, but as I grew up and got a real job, I simply didn't have the time anymore. I don't even build my own computers anymore, I did build my HTPC, but that was a project that stretched over the course of a year.
I also wanted to ditch my desktop. I was tired of being confined to one spot for my computing. However, I realized that there were still going to be some PC games I wanted to play. So I made sure that when I bought a laptop, I didn't go the cheapest route and got something with a little kick. To start with that was my Inspiron 6000 with a Radeon X300. Not very fast, but it played everything I threw at it just fine. I played through C&C 3 on it. Then my MacBook Pro. GeForce 8600GT. Plays everything great at the native res of 1440x900 (though, I haven't played crysis on it... It just doesn't interest me) and I'm currently trying to catch up on Sam and Max Season 2.
My advice, IF you're a die-hard PC gamer whose simply fed up with trying to keep up with the joneses, a console, coupled with a modest PC with a graphics card that can at least play a little something is the way to go!