Personally I can't say who the best rapper is at the moment, but I can list some of my favourite. I cant listen to none of that young thug, rich homie quan bullshit by the way.
Joey Bada$$ - So young has soooo much potential
Kendrick - G.O.A.T?
Mick Jenkins - Not very well known but so good. He is slept on for sure
Old Kanye - Shit now but was a great in college dropout phase
Biggie - Nothing to say just a legend
This is just a few but tell me if you fuck with any of these and some people I should listen to always open too suggestions for new artists to listen too.