Let's just lay out the GPU hardware for the consoles:
1. PS3 - gimped & modified nVidia GeForce 7800 GTX.
2. 360 - R600 foundation of the ATI Radeon HD 2000 Series.
Take note - ATI and nVidia don't manufacture those cards anymore, they are way beyond them for the PC.
About the only place you could find a HD 2000 series or a 7800 GTX would be eBay, but no PC gamer would install one in a Vista or Windows 7 PC.
Comparing today's GPUs from ATI & nVidia against what was made back in '05 is like comparing a steam locomotive to warp drive.:lol:
Let's say a PC user installs a 7800 GTX into a new PC - guess what they lose:
1. Direct-X 10 & 11.
The 7800 is Direct-X 9.0 (or older), and that's it, PS3 gamers.:P
It's heyday ended when Vista, DX 10, and the 8-Series GPUs came onto the market.
What about the 360, you say? Well, you can't run a PC on a R600 foundation alone, and no PC users would install HD 2000 cards into today's machines.:P
Neither console has the versatile control over their GPU like you do on the PC - screenshot below