I like the Govt Mule version of John The Revelator.
Beginning in the mid-1990s for about five years I listened to very little rock, almost exclusively blues. Read a lot about it, too. The late Luther Allison was my favorite. He was sort of a blues outcast in the 1960s and 1970s; purists didn't like his use of rock techniques like wah-wah pedals. He moved to Paris for nearly 20 years, returning to the U.S. in the 1990s to finally achieve commercial success and critical acclaim in his homeland with three excellent efforts on Alligator Records before he died. His final CD before he died, Reckless, was his best, in my opinion. He was not the best guitarist around, but he played and sang with a great deal of passion. His son, Bernard, is a bluesman, too.
If you like Clapton, listen to Freddy King and Otis Rush and you'll hear not only where he learned to play guitar but how to sing.
Hound Dog Taylor and J.B. Hutto are two examples of the "house rockin' " school of Chicago Blues. I enjoy both. Hutto's nephew, Lil' Ed Williams, is a lot of fun, energetic.
Of 1950s stuff, I'd recommend the Howlin' Wolf compilation "Moanin' After Midnight" as a good place to start. Also, Elmore James.
For really old stuff, try Tampa Red. He was big in the 1920s and '30s. His bottleneck guitar playing is pretty incredible.
