Probably Unreal Tournament 3. It's a really great engine... great graphics and will run really well on pretty weak hardware.
But, I really don't care about graphics anymore. All I ask is for HD resolution (720p and up), and that's basically impossible not to get in this day and age. I do most of my gaming on my PS3. The graphics on it certainly don't compare to most of its games' PC equivalents, but they still look great to me. The few PC games I do play, I play on my 15" Macbook Pro, and it handles everything to my satisfaction as well.
I think graphics are still improving. But, they've reached a point where the baseline is totally acceptable and still looks pretty damn good. It's a trend that makes gaming a lot more accessible. I still vividly remember the days of paying 700 dollars for a GPU alone just to be able to play the latest games. Now, I can get by just fine with a laptop...