I'm pointing out flaws in your argument, not taking a side. That is a commonly held view at TBD and in society in general. People automatically assume that because you're attacking their argument, that you must not agree.
Eminem does much more for hip hop and culture than being witty or humorous. His ability with words, syllables and literary schemes are unprecedented. He brought literary techniques that Redman, and any other rapper before his time ever brought. A typical verse rhymes the last word in each sentence. That is the basis for a rhyme. If you're really good, you can have a scheme of rhymes that matches up two words, and if you can get three lined up in each sentence, you're a genius. I've found patterns in Eminem's verses where he strings together numerous lines where's he's rhyming up to 5 words in a sentence, with each sentence having the words line up perfectly, all while making sense of the content. Each time I read or listen, I'm finding new ideas or patterns in his lyrics that I never saw before.
Throw in there the fact that because he's white, and how he was instrumental in bringing rap to the suburbs. With the white population heavily outnumbering the black, he brought rap back into the mainstream because he brought it to the nation's majority. Rap had lost all of that after the early 90's run, and Eminem brought in listeners who never listened before.
All of that is part of what makes him one of the greatest of all time, not just a one category rank system.