1.) He makes good albums, pretty consistently. His catalog isn't perfect, but his good material outnumbers his bad.

2.) He's able to leverage his relationships really well. Whether they're with Biggie, The Neptunes, Timbaland, The Roots, Kanye West, Jaz-O, Eminem, Linkin Park, Oprah, dream hampton, Denzel Washington, even Beyonce - anytime he has an ally, he almost always utilizes everyone's skills in a way that highlights his own talents, but that doesn't compromise his collaborators' integrity.

3.) He's ably reinvented himself the right ways, and at the right times. Whether it was the "hard knock life" transition, to the Blueprint transition, to the "living legend" persona on The Black Album; even when Kingdom Come was wack, he was able to establish the "grown up" persona well enough to use it on later records and for later press.

4.) He can make different types of songs. Girl songs, gutter songs, storytelling songs, a good diss song or two, shit-talking songs, etc. He's a pretty complete artist.