There can be no 'best' blues guitar player. Blues and blues guitar isn't poker, or chess.
However, you can ask "who is your favorite blues guitar player" or "which blues guitar player speaks to you the most".
I picked up the guitar the same week I heard "Texas Flood", so SRV was a catalyst for what has become a huge part of my life. However, without Freddie King, Albert King, Lonnie Mack, and Jimi Hendrix there would be no "Stevie Ray Vaughan" to talk about.
A lot more people have SRV albums than Albert King albums, but if you play someone Albert King that doesn't know any better, they might ask if that's SRV on guitar but who's singing(?).
Close your eyes and listen to this: