Next, I'd have to say Son House. Son played the slide that RJ perfected.
Some include John Lee Hooker in the Delta Blues. I personally disagree. John Lee's style was much different; more of a single chord style. And, he created the whole "boogie" sound. Much more of a free stylin' blues. I do rank John Lee as one of the all time best.
Electric blues...Buddy Guy, BB King, and T Bone Walker. BB has that signature style, and phrasing. Always in control. Buddy was the showman. Not afraid to take chances. T Bone, in my opinion, really started the the electric blues movement. Stormy Monday is classic.
Blues Rock...Eric Claption, Steveie Ray Vaughn, Jimi Hendrix. Seeing Eric Clapton live inspired me to get serious about the guitar. His tone and command is second to none. Stevie Ray's sound was soo unique; using a chorus efffect on a blues style was unheard of before him. Now, it''s everywhere. He could attack the instrument with ferocity, and then play it gently in the same phrase better than anyone. Jimi to me is the best guitar player ever. He could do it all. Straight blues, ballads, etc. His innovations with fuzz and feedback created a brand new sound. His songwriting is vastly underrated.
My Kid loved Blue's Clues when he was about 2-3. Thankfully, he grew out of it.