Well I listen to whatever I like. I prefer music that is unusual and original. But I also listen to what is consider mainstream too. I don't check charts for what is popular or not.
Anyway when it comes to mainstream music, its like they produce alot of "generic bands" that have one or two good songs but then the rest of their music sounds just like all the other bands before it in that genre. Also when something becomes popular record labels use that over and over until everyone is sick to the stomach with it. Well thats just my opinion about that.
As for the teenagers of today go, they all want to be accepted. Apparently the best way to be accepted is to show how independent and different you are. So the more unpopular your music selection is the more popular you become.