brief idea, partially stolen from ender's game:

MMOs with emergent levels of play.
For example: play levels of: presidents, generals, lieutenants, soldiers. The player of the president would have 5 generals underneath him, the general has 20 lieutenants, and so on. On the soldier level, the game is a first-person shooter; at the level of lieutenants, it's a real-time strategy game, at the general level, it's a turn-based strategy (at the level of Romance of the Three Kingdoms), and at the president level, it's a massively complicated game of Risk. The outcome of each level influences all the other levels.

Preferably, each game player would have a point value that would indicate their ability and experience; the higher the point of the game player, the higher he/she can go on the hierarchy of play levels.

Anything with interestingly defined emergent systems (that is to say, everything) can probably work this way. A virus game: Are you a giant ISP, a virus programmer/cracker, or the virus itself? And so on.

In contrast to Spore, this game would only be horizontally navigatable within each level of emergence..