Slim Shady to me was Eminem from 1999-2001, the time of the SSLP and MMLP. Each song save a couple were filled with some of the illest lines ever just for shock value. Then, you had the serious marshall in a few songs in that time span, most notably Stan.
Then the Eminem Show was the finest Marshall appearance we have seen to date.
Encore was the beginning of Muhammad Mathers, or the king of arab accents. Half the album was a masterpiece, the other an accented piece of garbage.
On Relapse, Eminem came back with the accents, but beefed up the lyrics. He brought back Slim Shady in an accented way, but fell short.
Recovery was Marshall v 2. It a average effot, but can not compare to the Marshall of The Eminem Show.
Eminem has three classics, and three O.K. albums. I honestly dont know where to put him as an all time MC. Top 5 from 1998-2003, and then a top 500 from 2004-2011...... Its hard.