My personal preference for AI behavior would also have two criteria, but those would be "difficulty" and "personality". Difficulty would basically make the AI use less varied, less efficient strategies. Personality would range from "efficient" to "plays for fun/excentric". "Efficient" AIs would try to win the game as quickly and as ruthlessly as they can. "Play for fun" AIs would just play, attacking once they've amassed a formidable army or things like that, use a wide variety of strategy (some not necessarily really efficient). Basically they'd be in control, so if you attacked them they'd retaliate and stuff, but wouldn't necessarily try to beat you as quickly as possible. The "efficient" AI would simulate a "real" MP game between players that want to win, the "excentric" one more of an MP game between two laid back players. But that requires a much more efficient AI than what we now have. For now, I agree with WhiteTreePaladin.