I'm assuming that you have alreayd played one of them: wikipedia help us with a good definition:
So, why i'm thinking about a god game?
God games come in a wide variety, from abstract or mathematical simulators to creative or conventional games. In most god games, the game is observed from an aloft, elevated perspective (Little Computer People with its side view is an exception). Many popular god games, like Bullfrog's Populous and Lionhead's Black & White are games of territorial domination while others, like SimEarth, are not. In some notable games, like Little Computer People and The Sims the player controls only one or some very few simulated individuals, providing for and guiding their lives, while in some god games the user plays a godlike entity that controls entire continents or worlds. In Black & White, the player guides a nation of up to thousands.
Because an idea of gameplay on MY mind need (IMHO) a category or better a way to think about my idea. Twisted, yes?
God game area incredible games, that try to create an equilibrium on high control and little control of simulation.
One good example of it is Tropico: player take control of an island in the middle of Cold War. You build you city-island, and take care of what people think about you, and how to manage economy, city, and so on.. incredible :D
But god games area really different.. but have one thing in common: player decide. Player can make difference with his/her actions.
Maybe an immediate difference, but most often difference in a long-game-strategy.