PC versions of console games have extremely high requirements compared to the hardware found in gaming consoles. If it were possible to install a PC game onto a PS3 or Xbox 360, those consoles would simply choke.
PC games pushes the performance envelop because new hardware is always being released. For example, just recently the nVidia Geforce GTX 680 has just been released. That is 6 generations newer than the GeForce 7000 series. Next month Intel will be releasing their Ivy Bridge generation Core i3/i5/i7 CPUs.
Gaming consoles are static. The hardware does not change. If you were to play a current PC game on a PC that was built 6 or 7 years ago you will be sorely disappointed.