I've always been a big SRV fan. There are many greats in the ranks of the old bluesmen and Buddy Guy has always been at the top of me.
A guy I've always thought was under appreciated as a guitarist is Prince. His solo on My Guitar Gently Weeps at the Grammy's which I think was for EC's hall of fame induction was just sick, he had some great guitarists on stage who were as staggered by his performance as the crowd was. SO many great talents lost too young.