Wow, this thread is still going. Good one, Jack!
If he wasn't mentioned already - let me add the late great Jesse "Guitar" Taylor. He lit up Joe Ely's band on many a night!
I agree that Lindsey Buckingham is underrated...I guess because he followed Peter Green. Also I'll second the mention of the great "Michael Picasso," Mick Ronson. What about Neil Young? He seems to squeeze such emotion into his playing and he has such a signature sound. For technical ability, I think Steve Howe is one of the great ones. Besides his work with Yes, he has done some wonderful acoustic work on his solo albums.