Not sure what your inputs are, but perhaps a rule of thumb (if not there already) is to generate a list of attractions sorted by quantity of reviews on (eg) trip advisor and then compare that result with #of people who actually go there.
It could give you the chance to rank 'must see' weighed against 'off the beaten track'. (Oz has heaps of 'off the beaten track' that the hordes of tourists don't know about)
