Bill Graham did a great thing in his San Francisco Fillmore Auditorium: he brought in many of the old blues guys that guitarists like Clapton, SRV, Peter Green, and Mike Bloomfield were copying. Seeing Albert King live really changed my perspective.
In the mid-80's I was fortunate enough to see Big Joe Turner backed by The Blasters in a small club in L.A. I wouldn't even consider trading that night of music for the two times I saw Hendrix, and Cream. I sure wish I had been able to catch Howlin' Wolf live, though.