Apple gives us to the developers the "power" to decide how the app is rated and which should be the minumum age of the buyer (not the player ¬¬) So i have been trying to be honest, but then I see games where you are killing people (lets say, Time Crisis) with a 4+ rating. Obviously Apple doesn't care. The publisher either. So who does? what is the real utility of the ratings?
Right now they are most likely meaningless. But should better parental controls come around, apple will definitely enforce these, so you might as well give your apps an accurate rating now.