I have 7800GTX Sli in my PC and have found that all multi platform titles are better on the PC - generally higher res textures, AA and better frame rate - look specifically at games like COD2, FEAR, Condemned, NFS:MW, Prey etc. I'm also running at nearly twice the resolution, 1680 x 1050, so the technical specs of the 360 are largely irrellevant at the moment as the 360 is not hitting them.
The only exceptions tend to be Ubisoft - GRAW, R6 and SC - where they are obviously developing titles for the 360 and doing completely amateurish ports to the PC for whatever reason. These are not optimised and need countless patches - foertunately the games tend to be crap these days anyway so no great loss.
The only 360 game that has "impressive" gfx is GOW but you have to remember that is a fairly basic game - run to an area, shoot, run to the next area etc.
What will be interesting is when we start to see DX10 stuff on the PC and how the 360 copes in comparison.