I have to say my PS3 is spoiling me a bit....when the first game you get for a new system looks like RFOM, you get some pretty high expectations. Playing FEAR right now, and I was actually struck by how smooth and nice everything was, not to mention the awesome lighting, but also kind of bland compared to RFOM, despite being WAY better looking than any shooter I'd played before RFOM.
Also, I would chalk up some of R&C's graphical prowess to Insomniac's having developed RFOM....but I don't have any explanation as to why Resistance looks so good.