And all I hear in nearly EVERY rap song is fast beats and people trying to get as many words out of their mouths in 3 minutes. No skill is required.
Even if you suck at singing, you can use some machine to make you sound better.
Lollipop is a terrible song.. a lot of people that know nothing / dislike rap seem to like it though, reason being - it isnt rap. Try listening to something a bit different. Hooks and beats are what usually get my hooked on a song so find some that you like and maybe you'll answer your own question.
I don't like rap but I used to so I'm guessing people like it because they say lyrics and because they like drum, bass, and computer sound instruments as a beat.
I don't understand that you don't know this question you are asking, Rap isn't about the artist or there voice, it's all about the lyrics and the way there written, if you want a great rap song to listen to for lyrics listen to , "Wu-tang clan - Punishment" it's a great song.