This should be a good thread. I don't know who I'd use for top 5 in either category, cuz I haven't given much thought to it since there's so many to consider. But my number ones I know for sure.

Rapper:
1) Tupac

Producer:
1) Dr. Dre

I think Pac will forever be number one on my list. Mainstream rap has been going down the tubes for the most part ever since he's been "gone" and I don't see it coming back up anytime soon. I'm bout sick of hearing what size rims all these rappers put on their cars and how much jewelry they wear and how many heads they bust open. Almost nobody comes with the real world shit like Pac did anymore.