[driftless]

Thanks for mentioning Watson and Rice. There's a few more in the pantheon of folk, bluegrass, and country pickers like Norman Blake, Dan Crary, Clarence White and a number of others who are heroes to the unplugged set. But it's obvious that most of the people taking part in the poll (or on this forum) believe that there is only one kind of music---loud rock and roll---and the louder, distorted, and more atonal the guitar the better. Congrats for having a good deal of taste.

[Jonah Johansen]

Problem is the term "greatest" is meaningless in this context.

What are the criteria and how do you weight them.
Speed? Technical virtuosity? Origianlity? Influence on other musicians? Should credit be given to song/melody writing ability? Showmanship? Energy level of live performance?

If you wanted to do a poll without clear criteria; I think your most accurate method would be polling the top 50 highest paid studio musicians in LA or at very least polling people who actually make a living playing guitar not wanna-bees and air guitarists.