LOL, no rapper will touch Eminem's success during his prime (99-02). But, that doesn't mean Kendrick won't be bigger than Eminem is since his comeback (09-now).
I know people who are HUGE fans of Eminem but they gladly admit that Kendrick is the best rapper out right now. Section.80 is known to be one of the best rap albums of the past few years and I'm sure most people would rank it way above Recovery or Relapse.
The fact that Kendrick missed the first week sales of SSLP by only 41,000 copies just shows that he will sell a lot more with future albums.