These are some of the most underrated guitarists imo:
Denis Azabagic (Have you heard him play la catedral)
Narciso Yepes (Who can as much clarity, punch, and definition? Listen to him play bourree bwv 996 and bwv 1000)
Dave Murray (Why does Adrian Smith get more attention than him? Murray is at least as good and I surprisingly never heard anything about him or Adrian Smith on this forum)
Mike Martin (Superb right hand technique)
Oli Herbert (Great solos such as the one in Two Weeks)
Brendan Small (Have you heard thunderhorse?)
Dino Cavares (You guys just don't like him because he's fat and Mexican. lol.)
Ray Toro (Everyone will probably disagree about this one, but I think he deserves more attention.)