It really doesn't though. I keep going back to last generation, but it's useful IMO. The Xbox 360 was a lot easier to develop for than the PS3, and PS3 games were a disaster in the beginning. Over time, the SDK got better, the tools got better, Sony optimized the OS and returned more RAM to developers and, lo and behold, the gap did get closed. That doesn't mean that 360 tools didn't improve to, or that 360 games didn't look better over time - just that the quality of the PS3's graphics improved at a faster rate than the Xbox 360's. Compare say, Gears of War 1 to Resistance 1 and then Gears 3 to Uncharted 3.