It's not that posters here aren't giving credit to Kanye. When looking at who he's being compared to, Kanye doesn't measure up. We're talking about producers who have influenced and impacted three decades of Hip Hop. When we're looking at Dre, we're looking at someone who has produced albums that are more legendary than anything Kanye has done. Dre has introduced Hip Hop to some superstars with his production. We're talking about artists who were either underground or virtually unknown before Dre. Not only that, but just look at the blueprint that Dre and Yella created off NWA alone.
In regard to Premo, he's lived up to his name. He's produced key records on some of the best rappers' debuts (premiers). Not only that, but Gangstarr is a legendary duo. Then you have his work with Jeru and Group Home.
That's not to say that Kanye hasn't put in work. He is a Top 10 contender, but when you compare him to producers who have put in the amount of work that Dre, RZA, Premier, and some others have done, he doesn't make the cut in a Top 3-5.