I think every genre is about 20% pretty good, 5% great, and 75% good-terrible.
In my opinion, about 1% of the great music is on the radio, the other 4% you have to find.
People pick on rap but there is some really good stuff out there. ie: black star, blue scholars, a tribe called quest, el-p.
Also, there is some really good folk music. Folk being countries older, more detail oriented brother. The mountain goats are amazing.