Interesting thread. As tricky to fathom as 'best guitarist'
Honourable mentions for:
Ryuichi Sakamoto (especially work with David Sylvian)
Ivor Cutler (spooky harmonium)
Jan Hammer (Mahavishnu Orchestra rather than film scores)
Dave Sinclair (Caravan)
Dave Sinclair of Caravan
Robert Wyatt
Guy Evans of VDGG
And if charm and originality isn't enough, the virtuoso madman of all time was Jan Hammer during his Mahavishnu days. Check out Birds of Fire.
Some of the suggestions on here are pathetic. I enjoy a bit of duran but to cite the...