Whenever I see debates on YouTube about whose music is the greatest- who's the greatest guitar player, does shredding suck, does the blues rule all, and how much do we hate/worship Hannah Montana- it makes me realize that I'm so much happier than those people, simply because if I summarize my opinion of music, it is this:
All forms of music are equal. The only real way to judge music is to consider the level of performance quality and the sincerity therein- and even those are matters of opinion, for the most part.
Also, the only quality I really look for in any kind of music is sincerity. Do they mean it when they sing and play, or is it just made on an assembly line? Even when the music is commercial, I like it if they focus on pleasing the customer rather than making money. The only thing that really turns me away from a group or musician- besides being boring, insincere, or poorly played- is if they glorify violence and/or lustful sex, or encourage worshipping Satan, which I object to on principle. I'm not too crazy about bands who're angry all the time either.
Everything else is fair game.
(I do make an exception with The Shaggs, who are notoriously terrible musicians. They're just so... sincere! Yeah, I know, I'm using that word a lot.)