I'd say the rapper who did the most of his career is Eminem, hands down. He grew up in 8 Mile, being white, no job, no friends. His parents didn't love him (his dad left him, mom sued him). He turned that around and rapped about it. Now look at him, tons of friends, happiness, money, etc.
Lil' Wayne is a good rapper, because he knows what people want to hear.
Other good ones: Illmatic, Wu Tang Clan, Snoop Dog.
Fastest rapper? Krayzie Bone (yeah, theres others, but you can't understand them.
[ame=
https://www.youtube.com/watch?v=LiF5PrMJEDU]YouTube - Krayzie Bone Heated Heavy (Runnin' With the AK-47)[/ame]