There are some very good game on the XBox 360, of course, like Oblivion, Fallout 3 etc... but an XBox controller can't and will never equal a PC keyboard in terms of numbers of controls avaliable and modding potentialities...
I think a time is coming for XBox 360, ( and others ) that is not so far away, that it will be more and more difficult to innovate, just because of these limitations.
But people go for the not so cheap ( after all ) but easy. Plus a PC is more sensitive to CTD, or at least should I say, not everybody is a computer geek, or even less than that... As a comparition, I'd say there's as much difference between them as there is between reading a book, and watching the TV....
As for Microsoft FSX, I have 250 planes installed, and is a permanent resident program on my PC ( excuse me !! ).