Take the engine and player interface from mass effect (bioware, KOTOR, etc) and instead of creating a universe and writing a backstory, use human history instead. If done correctly, the ability to choose different responses and paths allows the player to navigate our history, and create an alternate universe of the immediate future. Think sixth day movie meets back to the future, only you get to alter time/space. It would be insidious, teaching people about history, or at least making them do a little research...