In order to be considered a “Top” rapper you have to have top notch beats from top notch producers. To get top notch beats from top notch producers, you have to prove that your lyrical skill is worth their time. Sure, they will take a nice check for their services, but at the end of the day greatness wants to be affiliated with greatness. That has to be the reason why Common is one of the few rappers walking the planet who can say he has worked with DJ Premier, J Dilla, Kanye West and Pharrell and actually made classics with each one of them.
How many rappers can you name that have made better songs than these with these producers separately or collectively? Not that many.