You need to clear up what you mean by "lyricist"...cuz as far as a true-form lyricist, practically nobody listed yet is a lyricist, besides Del and Zion I.
Cats like Yuk and 40 can spit and can rhyme, but they aren't really lyricists. It's like calling Lil Wayne the best lyricist out. He's nice with the rhymes but isn't a lyricist.
So I'd say Del or Zion I