In terms of bad vs. good, though, music is like a lot of things in life, so subjective that you can't judge another person's taste. If for no other reason than people care about music to wildly different degrees. I've met people who say they don't listen to music. As in ever. Others cannot let a minute go by without having something playing in their head. It's akin to judging taste in food or recreational activities or movies. It's not really about what's good, rather, what gets a positive mental response.
That point aside, I'd say that what would be interesting is measuring how broad a person's musical tastes are. I.e., how much have they been exposed to and how much of that have they assimilated into their regular listening rotation. Pandora does a pretty good job suggesting artists I've never heard. When I hear one I like, I'll incorporate some songs into my regular rotation on Spotify.
If you must know, I have Bad Taste. The bad as in Hawaiian shirt-etc.-etc.-etc.... bad.