Just thought of a couple of others nobody mentioned...
Dead Rising was pretty revolutionary, because up to that point no one had put that many independently acting NPCs on the screen at once. Furthermore it was also impressive that you could basically pick-up and use anything you saw around you.
Halo 3 honestly had some pretty impressive technical acheivements as well. The way the matchmaking, movie making, forge and online community were all brought together and so seemlessly polished, you have to admit its at least somewhat impressive. Oh also I believe it was the first console game with 4 player online co-op within the main campaign.
Finally, i'll mention far cry 2 and Assasin's Creed here, because in order to have an open world game be that pretty and run that smoothly, you have to be doing some pretty impressive things with your engine. Far cry also wins bonus points for their work on fire burning in game, not to mention the incredibly impressive map editor. For as much as i have mixed feelings about Ubisoft, they have some damn talented coders f'sho.







