To troll or not to troll? Hmm...
Anyway, music is all subjective. But my vote for best rapper in the game right now would be Lupe Fiasco. His wordplay is unmatched, his flow is versatile and smooth and he actually has content behind his music.
Kendrick Lamar is also very, very good. As is Childish Gambino. Eminem is still as good as ever, if you don't agree then I don't think you've listened to Recovery or Hell: The Sequel.
Which brings me to Royce Da 5'9". He's very talented and very underrated.
If we go the underground route then we have to mention Immortal Technique, Murs, and Pharoahe Monch.
Asher Roth is great. Andre 3000 (Big Boi, not so much, although he's getting better with age). B.o.B, Hopsin, Wale.
I'll probably catch some heat for this, but Earl Sweatshirt and Tyler, the Creator both deserve mentions.
Earl has some of the best wordplay and flow, point blank. Especially at such a young age. Don't sleep on him.
Tyler, the Creator gets a lot of criticism for being a "satanist" (hinit, hint: He's an atheist, doesn't believe in god or the devil) and having dark lyrics. So the fuck what? The fact of the matter is he has an off the wall delivery that is very unique and instantly recognizable.
There are tons of other great rappers... And way more shitty ones (Drake, Mac Miller, Rick Ross), but I'll leave it at that for now.
P.s.
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