Well it's debatable.
Illmatic is one of the best albums ever.Rakim's(Eric.B's)Paid in Full is also a candidate.Biggie's Live after Death also.Eminem's MMLP,LL Cool J's Mama said knock you out..A lot of albums are Best ever candidates...
In my book Eminem is the greatest ever and Nas is in my Top-10
7.Big Daddy Kane
8.Kool G Rap
9.LL Cool J
As about the King of New York again it's debatable.Rakim was the first who had that title,then Big Daddy Kane,then Biggie,Nas,Jay-Z...
But Jay-Z love him or hate has that title for many years and the most success.
As about Eminem you kidding yourself if you think that Eminem isn't in the same class with Nas,If you ask 1.000.000 people 900.000 will tell you that Eminem>Nas.Do you remember Vibes voting last year?Nas wasn't even in the Semifinals.Eminem was the winner of Vibes best rapper ever contest.Eminem was up against 2pac in the finals, and won with 67% after 1.000.000 people votes
Eminem has the most fans than any other rapper in History.Call them Stans or whatever you want but the reality is that Eminem has by far the most fans worldwide.
Nas is Great and I don't have a problem if you consider him the GOAT but don't dispute Eminem because Legends like Rakim and Nas respect him a lot.
"Em is nasty man, I tell people to this day...if Em was black...he’d be the next Muhammad Ali.” - Rakim
"I think that's one of the most exciting things hip hop can look forward to. He contributes so much lyrically and musically, he's amazing,"-Nas on Eminem's album release
Eminem with Rakim
Eminem with Nas