For me it's the environment. I look at the environment more than the characters. I don't care how bad the characters look as long as the environment is nice. Best example is Shadow of the Colossus. The environment/scenery is more beautiful Wander and colossi. IMO...looking at the scenery is more fun than playing the game itself. Sometimes when I want to relax but I'm lazy to go out, I just put on SotC, listento jazz or house music, then roam around the map of the game. :)
I also like the environment's graphics in Hitman games and Bully.