#5 RAGE
Image Credit: Electricblueskies
RAGE uses an experimental new technology called megatextures. It's capable of rendering gigantic textures—entire city blocks, even—without having any impact whatsoever on the game's performance. Framerate, as it so happens, is the most important aspect of a game engine according to RAGE's creator, John Carmack.
Provided that your computer can handle RAGE's gigantic textures, you won't even notice a drop in texture quality—which was a common cause for complaint among players who picked up the game on day one.