The whole point is that the intelligence is "universal." By definition, we are talking about a thing which is able to transcend what it knows. So to me, the whole point is to introduce a variety of environments so that it learns the truly salient knowledge that is applicable across many games. And the most important of facts is this: stay alive. We might be able to bootstrap an ai up to a self-aware, self-preserving, rational agent which can adapt to any environment.