What are some games that show off the capabilities of the Xbox 360?

What are some games that show off the capabilities of the Xbox 360?

Obviously the newest stuff; 'Lost Planet', and 'Gears of War' are just absolutely remarkable. When people see them for the first time and they're told that the graphics on the Playstation 3 are even better, they're like "I find that hard to believe," because when something really looks great, and you're told that there is even more technology that makes it look even greater, you're pretty much happy with the fact that it looks great already.