I dont think you can say who's best at guitar but merely respect each man for what they bring to the table. And I say this as a musician with 15 years of experience playing brass instruments, 5 fucking around on guitars. Some guys are good at making ridiculously composed songs, like Tool and Rush, while others could improv for 4 hours straight without repeating a lick.

Bob Stinson from the Replacements was mentioned early on, he could have been great if he hadnt died so young. There's a legend that Paul Westerberg recruited him to the band after hearing him nail Texas Flood note for note when the guys were only in high school. Chalk up another loss to drugs/alcohol and the rock and roll lifestyle.

Chris Cheney from the Living End hasnt been mentioned, though he is the best guitar player in Australia. They actually have a competition once a year and he's won it 3 times in the last 5 years. He's one of those guys that doesnt play 100% on the records because your average listener doesnt want to hear nonstop guitar wankery.

Alexi Laiho owns at metal
BB King is probably the most influential blues guitar player ever
Clapton rocked at turning blues into modern rock
John Mayer is carrying this legacy on

Tom Morello shouldnt even be on the list since we're talking about guitar players, not distortion pedal players. He's good at innovating new sounds and techniques but not too technical of a player

And to the guys who credit Pennywise's guitar players, have yall heard Strung Out? Much tighter guitars.

But my vote for the best ever would be Jeff Beck. This man continues to push the limits on what is capable with an electric guitar and rock music in general. Who needs guitar picks, Beck sure doesnt.