on slim shady's quantitative self-assessment

Eminem (I know, I know) came up on the RealJukebox playlist at home: "The Real Slim Shady," from his second album. I spent the walk to campus mulling over the following lines:

I just get up on the mike and spit it
and whether you'd like to admit it
I just [excretory metaphor for the production of rap music]
better than 90 percent of you rappers out there
and then wonder why these kids eat up these albums
like Valium

The strange thing about the fourth line is how modest Eminem is (or his Slim Shady persona, I'll admit I don't really understand how that little narrative device works). I mean, here he is, even at the time the biggest selling artist in rap music, and when asked to account for his success, only places himself in the 90th percentile of all those out there doing that style of music. Imagine Tiger Woods denouncing his detractors by saying just that "whether you like to admit it, I'm better than 90 percent of you golfers out there." Granted, as an explanation for how you get to be the top figure at your craft, it seems a little wanting to say that you are better than all but 10% of the many people out there who do it. I wonder what he thinks is the rest of the explanation of his success--what propels him past those 10% of rappers who are by his own implication better than he is. In the same song, he goes on about how he has the [masculine anatomical metaphor for courage] to rap about things that other people "joke about with their friends" but are too afraid to say in public, so maybe that's it. Or perhaps he believes that it's simply a matter of luck, and the only reason this explanation didn't make it into the song is that "stochastic processes" doesn't make an easy rhyme.