Here's an interesting side-by-side of an early and later build of Call of Duty 4 on the Xbox 360 and then the PS3 (hit the jump for the second pic). While not meant to display the graphical prowess of each console, you can learn a lot about graphics design by viewing the evolution here. Aside from the obvious colour filter, look at the added detail in the PS3 balconies, the less blocky nature of the back building and the tweak of the left building to become less a pile of rubble (surely to alter gameplay options).
From the developer:
Every level goes through at least one "detail pass". The designers will rough in geometry and do a certain level of detail, but it's the environment artists that really make each level shine. The version of the level shown in the PS3 shot has been through one or two more detail passes than the one shown in the 360 shot.
The end effect, even shrunk in our pictures here, is that the entire feel is far more complete. Tiny design details will drive the future of graphic believability as much as any amount of texture or restraint with bloom lighting—just has Hollywood decorates sets far more than a student film would.