I gotta to with Eddie Van Halen. He's prob inspired more young guitarists than anyone in my generation (gen x). Most Underrated is Alex Lifeson. Rush spotlight usually falls on Neil but the two guys up front are unbelievable musicians also.
SRV is another favorite of mine. His voodo chile in the link is just unreal. That sound is killer!!!
I hate the "top xxx guitarists of all time" lists. there's too many greats. Same with every other musician. Drummers, bass, keys, obo.