The issue is that you can never judge music on any scale, only on your own. Go to all the classical rock fans and ask them about the best; hell, ask anyone about the best technical guitarist and a lot of names come up. You can perhaps condemn some extreme idiocies (like half of hip hop and britney-pop), but nevertheless.
Besides, even amongst teenagers, most intellectual ones will dismiss pop and hip-hop as horrible affronts to sanity.
Since everyone's talking about Metallica.. I should hardly think that their orchestral combinations were not musical, or not skilled; and their good albums (pre-Black Album) easily surpass the musical ability of.. Blink 182.
In the end it doesn't matter what education musicians go through or what genre they belong to, as long as they compose their own music, they express their own emotions, and they do it well. (of course, musical greatness is yet to be seen in some genres. )