Let us say that a possible world is unsurpassable if there is no possible world which is better than it. (This allows for the epistemic possibility that there may be more than one unsurpassable world, as opposed to the term “best” which is commonly understood to presuppose uniqueness.) Now, suppose for the sake of argument that (roughly) the God of traditional theism—an incorporeal, omniscient, omnipotent, omnibenevolent (etc.) being—exists. The question I want to examine is this: If God is infinitely good, not just in the sense of being omnibenevolent but also in the sense that God is of infinite value, is every possible world in which God exists an unsurpassable world? The answer depends on what we take into account in assessing the value of possible worlds. I see at least two ways of carrying out such an evaluation.
On the first way, we ignore any weight that might be assigned to the goodness of individuals and simply regard one possible world as being better than another if and only if the set of all good things which exist in the latter is a proper subset of the set of all good things which exist in the former. In this sense a possible world which contains God and one sentient being is—assuming all sentient beings possess at least some value--better than a world which contains God alone (not counting necessarily existent abstracta), and this is so quite irrespectively of the fact that God is infinitely good. It seems to me that there is no unsurpassable world in this sense, for given any possible world w_x there is always another world w_y such that the set of all good things which exist in w_x is a proper subset of the set of all good things which exist in w_y. On this view possible worlds can only be ranked according to their goodness, one cannot say how much better one world is than another.
According to the second way one should take into account not only the number of instances of goodness but also, so to speak, their intensity. For when we say that God is infinitely good we do not (or should not) mean that God has aleph-null (or some other transfinite cardinal) units of goodness, but rather that God’s goodness is “infinitely intense” or “unsurpassably intense”. We might characterize this by saying that in our moral considerations God’s goodness ought to be given an infinite and/or unsurpassable weight. Given that God’s goodness is infinitely or unsurpassably intense in all possible worlds where God exists, it appears that taking the “intensity” of something's goodness into account in determining the value of possible worlds yields the result that all possible worlds where God exists are unsurpassable.
So it seems that if God exists either none of the worlds which God can actualize are unsurpassable or that all of them are, and in neither case is there a unique "best" world that God can actualize. The interesting question is then, if that’s so, does it follow that God must choose a world to actualize at random?