He is easily the most overrated rapper of all time. His flow was average at best, his lyrics lacked complexity, metaphors, punches, multi syllabic rhyme schemes and word play. He was decent as a story teller but there are many who are much better. If you compare his skills to all time great mc's such as Rakim, Kool G Rap, Nas, Big L, or Biggie, he isn't even in the same class. Pac would shine in an area such as spoken word poetry but not as a great mc.
Pac had lots of heart and great energy as an entertainer. If he had lived i'm sure he would have developed into a really good actor.