I'm not sure, but being a blues nut I own just about everything Freddy King, Robert Johnson, T-Bone Walker, Muddy Waters, et al, recorded. I also have most of Clapton's works in my collection - including the seminal 'From The Cradle', in which he pays a worthy tribute to the greats.
To be honest, I'd be happy (or been happy - many of the greats have moved on) to take a lesson from any of them, and even though I'm not a huge fan of Gary Moore, I'd kill for a session with him.
Everyone has something unique to give...