The problem with democracy games is the more democracy you have, the less potential for fun the player has. Essentially it involves decreasing both the control and power of the player in a way which only makes sense when those who take up those responsibilities are actual people, not RNG AI. A multiplayer democracy game could be fun. A singleplayer one would probably get very frustrating very quickly due to the limitations of game AI being very obvious in situations which at their very core are based on the way humans think and act. Especially since most players would not act like your typical IRL ruler due to the natural risk/reward skewing of video games. Most people want action and intrigue in their games, not political demagoguery towards an imaginary public.
Just look at Obama's job. He little power over the government as a whole due to checks and balances (although some aren't exactly in a balanced state), he makes a few decisions, gives speeches which are almost all written by someone else, and if he did go nuts and do crazy stuff for the lulz he would be locked up before almost any harm was done. In a game, players generally want as much control as they can get, don't want an RNG interfering with their plans, and want to be able to go absolutely batsh*t insane for the lulz when they get bored. And they sure as hell don't want to have to do grandstanding for 2 years to pass something as mundane as healthcare reform for an imaginary group of people.