
Not the lightest reading, but very worth the effort. TL;DR - taste is something that can be more refined or less refined. We have some reasons to believe that more refined tastes are 'better' than less refined tastes (people who have learned to appreciate more sophisticated tastes never want to 'go back' even though they now have fewer opportunities for enjoyment).
Obviously it's very controversial and you can make the argument that it's just snobbery, but I think Hume gets at something.
There's no easy way of answering that on this kind of medium (an Internet forum). I took two graduate seminars and wrote several papers on it :) But as a primer, I strongly suggest reading Hume's 'Of the standard of taste': http://www.econlib.org/library/LFBooks/Hume/hmMPL23.html
In that essay, he attempts to provide some clear-cut criteria for an objective judgment of art, food, and literature.
(Note that there ARE people that are relativists and they have a somewhat compelling argument. That's perfectly fine. I just don't buy it and I think they're wrong.)
As I suggested in my other comment, as I primer, I strongly suggest reading Hume's 'Of the Standard of Taste' and bringing forward some talking points instead of pretending like you're making some kind of profound argument. In other words, what you're saying isn't new. It's also very simplistic, naïve, and (I believe) probably wrong.