[saghm]

I'll second this; while I haven't played them myself, I've watched playthroughs of all three of them, and they really do an amazing job of blurring the line between the player's character and the real-life person playing the game. Combined with having some hidden secrets being only unlockable by doing real-world things outside the game, it's hard for to decide whether he's basically created a new art form that transcends the game genre or just has gotten everyone who's played the game essentially to join a sort of AR/roleplaying game of which his video games are just some of the pieces.