I'm gonna get a lot of hate but at his peak Cam'ron was something special. He created a whole lifestyle which dominated NYC for years. I still listen to Purple Haze often. His rhymes are simple and pretty stupid most of the time, but every once in a while he'll throw something into a verse that shows just how sharp he actually is. That's what I think is great about Cam, his ignorance is all a show and he was the best at boasting about shit which is a cornerstone of rap.
OH, and Big L was great too.
Also, how are people talking about wu-tang but not mentioning GZA. Liquid Swords is easily lyrically/conceptually my favorite wu record.
to me Mos Def was always more of a musician than a rapper, if that makes any sense. He's a great lyricist, don't get me wrong, but he used his voice to create melody more often than to display his clever wordplay or imagery.