This isn't here just because Diablo 3's release is right around the corner - but because of all the game's I've played recently, this is the one I have the fewest complaints about, game play wise.
Blizzard struck gold with the first Diablo, a more or less left-click oriented adventure that kept people running the same dungeons and playing the (relatively) same game over and over, for hours, hoping to find better gear for their character.
The gear-oriented infection of gaming ensued, and is the unholy predecessor to the majority of games we play today. Simple yet elegant game play that leaves very little up to interpretation. You know exactly what's going to happen as you make your decisions throughout the game. It's hard to come up with a complaint about Diablo's game play.
