Most people prefer them... so.... does it matter who's the best?
If more people prefer my work than whoever "the best" is wouldn't that technically make me the best? At the end of the day the public decides what the best.
Rap is subjective. A majority of people prefer Gucci Man, does that means he is one of the best rappers? There is a lot of garbage songs on the radio that a majority of people prefer, does that mean these are the best songs out? Just because someone is a mainstream artist doesn't mean they're better than a underground artist and vice versa.