The requirements to run the latest and greatest PC games are just insane. Many of them, at least. I think we long since passed the minimum bar threshold for running at 30 frames-per-second, and now we're just paying the price of being a second-class platform.
I'm guessing one of two things may be happening
(1) console games for the PS2-3/360 are getting sloppily and quickly ported back to the PC, without taking the time to make them efficient for the PC architecture.
(2) video card / cpu companies are somehow encouraging this mess in order to drive sales of new computers, in a time when sales are slumping because machines are already ridiculously over-powered for the average consumer.
just an idea. i'd love to see more games ported WELL to the PC. a criterion collection or Mobile High Fidelity for the PC gaming industry.