But in rap, rankings like this take on a special level of import: aside from moving a crowd (shouts to Rakim), MC means proving you’re the best. In no other genre do artists so blatantly express their desire to outdo competition. That made Billboard's editorial list a more high-stakes undertaking than usual. Many favorites -- Kane, Drake, KRS -- didn’t make it, and each of those omissions hurts deep down. Note: we’re ranking these folks as MCs, not artists. That’s why Dr. Dre and Kanye West, for example, two legendary producer-rappers who don’t match the mic skills of those listed here, were left out. Even Tupac, perhaps the most influential rapper ever globally, is arguably known more for great songwriting than dominant bars.