Don't be silly, I listen to classical, jazz, classic rock, 80's rock and pop, alt rock, reggae, motown, japanese classical, techno, punk, industrial, 90's gangsta rap, prog rock, even a little country, and the hardest metal I can get my hands on. Hell, I'll even tolerate a little Lady Gaga. I'm a huge Tom Waits fan. I love U2, and they're pretty much the most 'mainstream' rock gets. Metal is first for me, but there's no reason I shouldn't enjoy many different types of music. Sure there's always fad groups, but a lot of times music is mainstream because its good.
I mean how much more mainstream do you get than Mozart? That guy WAS pop music in his day.