What impresses you the most in a game?

For me it's lip synching and facial expressions as well as how tight the controls are. I don't really care that much about the former, but I really like it if the game I'm playing does it well.

story, cinematics, graphics, polished gameplay.

any game that makes me not put the controller down at 3 a.m. (playing since 9 p.m.) on a school night with two or three tests the next day....