This is a tough question. The list will be based on each user age group.
For me. Eminem, Kendrick Lamar, Vector are the three greatest. Eminem with the way he raps is easily everyone choice. A legend in the game churning out awesome lines, verses in every songs released. Kendrick Lamar
You just have to love him. He's one of the best rapper of recent and he's destined to be a legend in the game.
Vector is a local artist who is making waves. He recently tried to break the world record for the longest freestyle rap of 13 hours. He's a good rapper with a lot of punchlines in his songs.