This is THE big question in aesthetics. And its among the most difficult questions in philosophy. The problem is that we all, and especially artists, assume that some works are better than others. But this also somehow feels wrong because how could we compare a Maya Fresco and a Fra Angelico painting? It’s like comparing apples and oranges. My own view is that all such comparisons should be indexed to a cultural background of the comparer. I hope this helps.