God, ostensibly, starts with a "blank slate." He then decides to create reality, and being all-powerful and loving, He decides to create the best possible reality for us to live in. Thus, this premise predicts the world we find ourselves in is the best (i.e. produces most happiness) of all possibilities, and thus we cannot imagine a world better than it.
I'm arguing that's absurd, by citing the counterexample of Pandora. It is quite obviously a better world to live in, and so any premise that concludes that Earth is the best of all possible worlds is unarguably wrong. James Cameron is better at inventing a world in which the inhabitants are happy than Yahweh, if we accept the premise that Yahweh created the Earth.