I agree with those who feel there is no "Best" blues (or any other idiom) guitarist. For every name I can come up with someone will have one that does it better. Everyone's style is different and what appeals to some might not float your boat. I do feel though that Clapton's style changed over the years and moved away from the blues guitar playing he was so good at early on (with Mayall's Bluesbreakers and others)to a more commercial popular style. His hero early on was Freddie King. These days I happen to like Ainsley Lister, Lightnin Malcolm, Studebaker Bob, Chris Cain, and Guitar Shorty.