What draws me back everytime is how different each game is. It begins with the infinite combinations of race traits, then the local star systems around you, are you isolated? Short on food? Do you have to trade away your gold to stop the Insectoids breeding out of control and crushing your worthless yet peaceful under-developed civilisation? Do you grow strong from your expert diplomacy, or control though your technology? Will your civilisation survive the sometimes unfair conditions you are faced with or dissapear into the dust of eternity?