It's kind of crazy, I was a big fan and I'm still a fan but his fans who act like he created some unheard of thing and shaped rap are flat out annoying. He's a clever rhymer, has a cool flow and rapped about some things which are pretty uncommon but I've listened to his first couple of albums (which were his best) recently and they're pretty damn hard to nod your head to. These were his great albums and a lot of it just doesn't hold up all that well for me. I haven't even liked most of his stuff in more recent years.
The stuff I love from him is songs and verses he's done on things like Soundbombing and collabos with others, "The Sauce" is one of the best diss tracks of all-time. Basically he's a great rapper who is lyrical and extremely clever but nothing he's done hasn't been done before. There are plenty of other rappers who are more lyrical, with bigger vocabs.
He's up near the pantheon but there are just guys who are better. Marshall Mathers LP is clearly his best and there are a bunch of other rappers who have stuff that blows it out of the water.