Guys, I'm willing to bet that Ted will be along soon... anyone wanna take me up on that? Lol
Anyway, Will doesn't get the respect he deserves in hip hop largely because of the content of his music. Hip hop has become a culture focused on material things: ice, whips, clothes, and women (considering that are often treated like objects.) Will's never been that kind of rapper, but since that's what the culture is infatuated with, it is undoubtedly be hard for an artist like Will to do well. The lack of "hard hitting lyrics" is another reason he doesn't get much love in hip hop. The lyrics in songs have become so profane and lewd that it's gotten to the point where the absence of such lyrics is seen as abnormal. There's a notion that if anyone can listen to it, it's not really exciting. The more lyrics push the envelope, generally the more popular they are.
There are, in fact, a number of reasons why Will doesn't get much respect, but those I addressed seem to be the most glaring examples.