The perfect game for me would be a sci-fi, with tons of politics and social order. It would be like a MMORPG, but it isn't imbalanced with a levelling system that is stupid (like WoW/etc) but is based on the actual skill of the player. There are numerous different civilisations you can join, or even attempt to create your own, or cause a revolution, or destroy. It would be a totally open ended game with the ability to do practically anything. (realistic limits obviously apply)