I don't think he gets enough credit in these type of conversations. Probably because he is a DB and no-one can stand him.
Also agree with SRV and would throw in Clapton and Page. Hendrix will always be #1.
That and personally I find his music kind of cheesy. I had a co-worker who loved him and always played his music during the work day. The guitar work was excellent, but the over all music he wrote, imo, wasn't much better than a neighborhood garage band could put out.
For my over all view of best guitarist, it's so hard to nail down. With so many different genres in music you can't say one person is really the best. Hell, I saw Leo Kottke at the Mshop in the early 90s and was blown away by his work on the old 6 string.