Yes, a very tough one.
I picked Bone Thugs though, because Doggystyle is really a sequel to the Chronic and was basically spawned from an already existing movement.
Bone Thugs, though backed be Eazy E, was completely original and changed the game. Some will say that they ran with a style that was already poppin' in the Midwest, fast rappin, but not the Harmony part, that was new.