Some of my favorite blues are swamp blues. Originally on the excello label, their reissues are easy to find and are perhaps some of the best mono recordings around. This is due to recording genius Jay miller. Also, look at the flyright label. The artists include, Lightin Slim, Slim Harpo, Lazy Lester, Silas Hogan. Go to the Arhoolie website and pick up a CD Lousiana Blues. British Blues, Old Fleetwood Mac, and many others on the Blue Horizon label. Pick up the Blue Horizon Box set with the early Fleetwood Mac albums.
Other artists in the Chicago Blues class, Magic Slim, Earl & his cousin John Hooker, Tinsley Ellis, Walter Trout, etc. If you really want a good selection to choose from, listen to online radio 'live365.com Select the blues and the many categories the stations play. You are your best judge.