I saw Kendrick Lamar live not too long ago. I had fun but I think I need to listen to a lot more of his CD before I could say what I think of him in general. From friends of mine who are bigger fans, they do assert he's the #1 rapper out there, or at least, is going to be - one particularly ardent friend asserted that he is "the next/new Tupac." I thought that was quite an assertion to make, but I'm not familiar enough with rap to really have an opinion.
Personally, I really like Macklemore. I'm not trying to say he's #1. He's probably more like Eminem 2.0 or something. But I do think his songs have a deeper meaning that I find, at times, really inspiring. I like the fact that he seems to be trying to say something with his words (though you can probably make the same argument with Lamar).