Do you think the actual world contains the maximum possible amount of goodness? To clarify I'm not purposely not phrasing the question in the traditional way, 'Is this the Best of All Possible Worlds?', because I don't mean to imply there is only possible world that satisfies that condition - if there are goods which are different but commensurate then plausibility we can have any number of 'Best' tier worlds (and thus avoid modal collapse, albeit at the cost of being faced with a Divine variant on Burdian's Ass). 

A further point: the decision as to whether this a Best' tier world is not effected by the instances of evil within it, as the 'Best' status is ascertained by looking at the world as a whole of concrete history, something presumably only God is in a position to do. Indeed as the German pessimist Eduard von Hartmann observed the actual world could be unspeakably horrific and still 'the best of a bad bunch' so to speak (the implicit assumption here is that God does not have an opt-out option on creating - the classical theist will probably want to modify this with the caveat that any world God creates must have more good than evil).

Thomists don't like the idea of best worlds, probably because they associate it with the modal determinism which follows from Leibniz own account. I think they have points to commend them though