Heh, ok, first off, Xbox is nothing similar to a PC. It has some similar equipment, but it in no way can handle anything CLOSE to what a PC can. Just because it is built by Microsoft does not make it a computer.
I own an Xbox and a PC.
Secondly, it actually doesn't take very long to build a new engine. The coding, animating, sound, etc... is what takes all of the time.
Thirdly, the PC version WILL be very much different from the Xbox version.
Perfect example of this is Ravenshield. The Xbox version of RVS is godawful, the PC version is excellent.
You guys complain way too much about stuff you don't need to.
O, and just so you know, I bought an Xbox for Sports games and Racing games... that's it. Only thing a console is good for IMO.