Let’s start with Freddy King, he didn’t play a guitar he attacked the guitar!
Although he never attained any real fame or fortune during his lifetime I believe he more than earned a title as a bluesman.
Roy Buchanan
Green Onions Live Carnigie Hall Live
B.B. King Plays Live at Sing Sing Prison in One of His Greatest Performances (1972)
ERIC GALES
Catfish Blues
https://music.youtube.com/watch?v=nQtxg51Op_Q&feature=share
Guitar World Magazine’s Reader’s Poll named Eric as “Best New Talent,” in 1991. After recording a second record for Elektra, all three brothers teamed up for The Gales Bros. “Left Hand Brand” which was recorded for the House of Blues label in 1996. Through the years, it would not be unusual to look out in the audience and see artists like Carlos Santana, Eric Johnson, B. B. King, and Eric Clapton, looking on with interest as Eric took his guitar and worked crowd after crowd into a frenzy.
Well Curtis Loew was held in high regard by some fairly prominent musicians. 
He was in fact a a mixture of many of the small town blues artist that influenced Lynyrd Skynyrd. Their way of saying that the blues was best played by people that actually lived in the blues. Not to downplay the greats like BB King, but to acknowledge the roots of the blues.
I got to see BB King at his club in Nashville right before he died. He was awesome right up until the end.
Lightnin’ Hopkins. I love this short little instrumental of his; it’s a virtual encyclopedia of acoustic blues guitar riffs in just 98 seconds.
Earl Hooker: “Sweet Black Angel”
Brilliant.
To complete the “King” trio: Albert King. He’ll play the shit out of the blues for you.
One of my personal favorites - Son Seals
Robert Cray.
One of my personal favorites as well. I met him very late in his career/life (he toured until he died because he needed the money. He truly lived the blues.
From Wikipedia:
Seals had a hard life. He survived all but one of his fourteen siblings. In 1997 he was shot in the jaw by his wife, sustaining injuries which required reconstructive surgery.[14] In 1999 part of his left leg was amputated as a result of complications from diabetes. He lost belongings in a fire that destroyed his home while he was away performing, and several of his prized guitars were stolen from his home.[15] After his health began to decline, Seals toured with accompaniment by several different bands, including those of James Soleberg, Jimmy Vivino, and Big Jim Kohler.
Magic Sam (playing Earl Hooker’s guitar):
Robert Johnson, of course.
Bill Bill Broonzy:
Sonny Terry:
Sonny Boy Williamson I:
So many greats it’s almost a crime just to choose 1 or 2. Elmore James & Jimmy Reed haven’t been mentioned yet so I’ll add those names.
Comparative youngster Kenny Wayne Shepherd put together an interesting project several years ago titled ‘10 Days Out: Blues From the Backroads’, in which he & a camera crew along with a couple other notable names traveled the southern circuit to meet up with a number of blues greats, most of whom are not household names, to say the least. He listens & plays with them in their living rooms, kitchens & porches.
The project really belongs to the great artists who appear - Kenny Wayne was merely acting as the conduit. Many have passed on now due to age.
Available on CD and DVD. You really need to watch the DVD in my opinion.
Stevie Ray Vaughan. Chose this song and this performance because the tone he gets on the main guitar solo (starting at about 2m) is the meanest sound I’ve ever heard come out of any blues guitarist ever. It sounds like he’s playing through an angry beehive.
I’ve seen BB King live, I’ve watched some Freddie King on Youtube, but I think Albert is the one I really need to dig into more. There is a video (in multiple parts) on Youtube that has Stevie Ray Vaughan & Albert sitting together, talking & playing for 90 minutes. Really enjoyable stuff.
Albert was one of Stevie’s guitar heroes, so I imagine this was a big deal to him - though he did manage to play with most or all of his heroes before he died.
Roy Buchanan was mentioned already. He was a,“guitarist’s guitarist”, widely respected, but never found much fame. I saw him live, one of my favorite concerts ever. I lived in Pittsburgh for awhile, home to Billy Price, who was Roy’s vocalist for three years and one album. Here’s Roy and Billy on, “Can I Change My Mind.”
And here’s some of Billy Price’s later, solo work: “Who You’re Workin’ For.”
Billy Price is still performing, one of Pittsburgh’s best, along with Norman Nardini.
Is Norm still singing that damned, “Smoke Two Joints” song? Guy sings more about weed than Snoop Dogg 