Of course rankings are always biased, blah blah blah. But, what makes this website great is that it is one of the least biased music rankings you will find. I'm not really sure how it comes up with the rankings, but the majority of people seem to agree with them. There's music lists on almost every genre, including Rap, Disco, and Electronic.
Don't use the website as a stone-cold list, but use it to discover and appreciate top music artists that you may have never heard of before. For those about to rock, I salute you.