You're a fool for thinking the likes of RATM or Bob Marley are mainstream, and even if they were (which they're not) how does that in anyway equate to poor music tastes? When RATM came out, they were different, it's only because they we so good, that they're now considered one of the best banRAB of the 90's. Bob Marley is a legend...
Coldplay are mainstream, but again, why does that mean their music is bad?
Edit: I only have AIC's Dirt album, but I think it's very good. Rooster, Bones, Would, Rain When I die, etc are all awesome songs.