I've had similar results with my old roommate with Halo. I couldn't win at Halo for shit playing on the Xbox, but once it was on the PC and we did a grand rematch with our normal Friday Halo group, I dominated as a PC gamer with mouse and keyboard. And I've never been very good at FPS games!
The console players got destroyed every time. So much so that it would be embarrassing to the XBOX team in general had Microsoft launched this initiative.
Just one more reason to be a proud PC gamer.