I don't understand why so many people wish this. It seems like people who feel this way exhibit a refusal to accept change. If you wan't SSLP, MMLP, or TES - go listen to those albums.
Eminem has shown growth with his material (with the exception of Encore)..although songs such as Ass Like That, My First Single and Toy Soldiers are creative in their own right. Eminem's voice along with his style and portrayal of emotion has changed. He's matured and even though you can argue that his new music is or isn't better then his old stuff, it's still on par with it.
Since his return, Eminem has proven and re-invented himself. I understand that I'll never get the old Eminem back but I firmly hold a belief that a lot of his new stuff is better than his old stuff. I really enjoy the new flows and the maturity that accompany his new style. Dude is on his game.
Personally, I think Despicable freestyle is the best Eminem track I've ever heard.