Future titles can, and will, in retrospect, make older games seem less impressive. It's happening now. That is not to say that in their own right, given their hardware, that PS3 and 360 games aren't pretty, but as you move forward, you will look back and see that they could have looked a lot better. This will always happen. When you're in the moment, you can predict that games will look better years from now, but you won't know exactly how until that future becomes the present, and when that happens, games retroactively lose their 'wow' factor.