I'm not a so-called purest, but when I think blues, I have to divide it up into electric/blues-rock, or pure, original blues.

For blues-rock, that would be Jimi Hendrix. He ran with it and pushed the limits like no other.

For absolute feeling in the electric blues world, Gary Moore.

For pure blues, Robert Johnson. Unlike the English invasion lads (who I love, such as Clapton, Jeff Beck, etc.), the original Delta blues was created by guys like Robert Johnson. The Chicago guys had the right feeling, but they came along later and copied/progressed upon what the first bluesmen invented. It all came from the past slave work songs they created in the fields.

I'm sure this could go much deeper, but that's not my intention here. I;m also sure I'm not 100% accurate, but you get the meaning.