Rakim is the best hands down

And to the person that said "2pac made Dr. Dre".... you dont know what your talking about. Dre practically started gangsta rap with NWA in 1987-1988. 2pac didn't get into the gangsta scene until 1996 (and only got into the solo rapping scene in 1991). In fact, All Eyez On Me with it's single California Love probably gave 2pac most of his current popularity. And it was produced by Dr. Dre.

And 50 Cent is NOT the greatest MC of all time. Not because he's mainstream, because he's crap.