Robert Adams famously argued that an unsurpassable being need not actualize the best possible world. Adams urges that he does not believe that there is a best world, but assumes there’s one for the sake of argument.
I think it is fairly plausible to suppose that God could have created a world that would have the following characteristics: (1) None of the individual creatures in it would exist in the best of all possible worlds. (2) None of the creatures in it has a life which is so miserable on the whole that it would be better for that creature if it had never existed. (3) Every individual creature in the world is at least as happy on the whole as it would have been in any other possible world in which it could have existed. (‘Must God Create the Best’, PR, 1972)