I'm working a little backwards here having read the later posts, but wholeheartedly agree with Big Al, and later posts including David Hidalgo, David Lindley, Bill Kirchen, Richard Thompson, Mike Henderson, Ry Cooder and many more.
Was thrilled to see Big Al join Los Lobos on-stage in Northampton MA 2 years back. Even David Hidalgo put hand to heart with Big Al's entrance. Cesar stepped it up a notch or two that night as well.
Haven't seen Jorma Kaukonen mentioned yet either....or Duke Robillard- This begs the question of the other blues guys..... and then there's David Bromberg too....
One more question though, are we including the first generation flat-pick guys? Doc Watson, Don Reno, Norman Blake, Tony Rice, Dan Crary, and then David Grier, etc?
To me, those guys are all first rate.