2Pac, definitely, not discussion. I'm more into rock and metal, but thanks to him I'm trying to learn more about rap/hip-hop and it's cultural impact.
2Pac was really talented, a prodigy, but the most important, he had always something meaningful to say, he understood the power and responsibility of his music, its impact on society, trying to make a change for better (not all of his work of course).
Currently, in my opinion, there is no one making music with an important social meaning and that also sounds as good as 2Pac did.