If you’re talking about great recorded sound alone, I second the Audioquest label suggestion. A long-time reference disc in the Blues genre is Folk Singer by Muddy Waters. Be forewarned: it is Rural Acoustic Blues, not the amped-up Blues you hear from more modern (and usually white) practitioners of Blues/Rock, such as Blues Hammer (inside joke ;-) .
It is an unfortunately truth that most of the best Blues (as well as other musical genres) was recorded in mediocre or worse sound quality. Howlin’ Wolf and Little Walter are fantastic, but their recorded sq is not. Holt’s Law: The better the music, the worse the sound, and visa versa.
