I downloaded the 360 demo just to see how it looked and I was amazed at just how lousy it looked in comparison to the PC version
Were you playing it in HD? I just recently came into some expendable cash, so I bought a 26" LCD HDTV and an Xbox 360. After playing 360 on an HDTV, I'll never go back to any other console (except maybe SNES). Granted my PC is beginning to age (about 2 years), but right now all the games I have for 360 blow my PC away in terms of graphics.
I like Prey. I haven't beaten it yet, but I've gotten a good ways into it. I think it adds some new ideas to the genre that others can build off of, which is what FPS is lacking in these days; ideas. There are so many shooters that come out that add nothing to the genre. So even a game like Prey that adds something in the ways of physics or graphics is welcome and appreciated, IMO.