Here's an extensive, but not exhaustive, list. To make it more interesting, I've added a few comments.
I think the ones marked * have not been mentioned in this post.
The ones marked # are not necessarily jazz.
The artists I rate most highly are marked with !
Adam Rogers (To be heard on Michael Brecker's Wide Angles album, though there is a lot going on so its hard to pick him out. I wish Michael well, by the way)
Ackerman, Will*# (Windham Hill artist)
Al Di Meola!! (Not so keen on early material, but everything since World Sinfonia is excellent. Also great on Jazzpana 1 and Chic Corea's Touchstone, and with Paco de Lucia and John McClaughlin)
Allan Holdsworth
Andy Summers* (Police fame. Eclectic player who plays some jazz as well)
Anthony Wilson*
Antonio Forcione*! (Comedian and great acoustic guitarist)
Attila Zoller! (I agree with the comment about him being underrated. A sad loss. One of Metheny's tutors.)
B.B.King
Barney Kessell
Bill Frisell!!
Bireli Lagrene!* (How insensitive not to mention him!)
Brad Schoeppach* (Plays with the great Rosenwinkel on a few Paul Motion albums)
Brad Shepik (Playing tonight in the 55 Bar, I see. Too bad - I'm in London)
Carlos Santana!
Castro-Neves, Oscar*
Charlie Byrd
Charlie Christian
Chuck Loeb* (He's got some chops. Not all smooth, necessarily.)
Ciyo Brown* (Best version of Little Sunflower there ever was on his "Somewhere Out There" album)
Dave Stryker
David Gilmore!!
Django Reinhardt
Earl Klugh*
Emily Remler
Eric Gale*
Erquiaga, Steve*# (Windham Hill artist)
Frank Gambale (Famous for 'The sweep' - a guitar technique).
Gene Bertoncini
George Benson!!
Gerardo Nunez# (Great flamenco guitar on Jazzpana 2)
Grant Green!
J.Yamagishi* (Another guitarist with Watanabe on excellent Dogatana)
Jack Wilkins*
Jeff Beck*!
Jim Hall! (An amazing track is "Careful" on "Jim Hall and Friends Live at Town Hall" with Sco, Bernstein, Goodrick, Abercrombie - all guitarists mentioned in this list _ Gary Burton. Also Jom Hall is a big influence on Metheny)
Jim Mullen* (Scottish guitarist, used to play with the late Dick Morrisey. Uses his thumb exclusively)
Joe Beck*
José Neto* (Impressive with Airto's Fourth World. Plays a unique guitar which also acts like a bass guitar)
Joe Pass
John Abercrombie! (Plays on one of my favourite albums, Landmarks by Joe Lovano)
John Etheridge* (Though he sometimes plays tucked away in small pubs almost unnoticed, he is very good. Played a lot with Stephane Grappelli. Also of Soft Machine fame. His album "Ash" is worth checking out)
John McLaughlin! (Love those guitar trio albums with Paco and DiMeola/Coryell. Great on hot summer nights)
John Parricelli* (Listen to his track 'Scrim'. British guitarist)
John Scofield!!
Jon Herington
Kazumi Watanabe
Kenny Burrell
Kurt Rosenwinkel!! (Wow! Saw him in Smalls 10 years ago.)
Larry Carlton
Larry Coryell! (The Kenny G of guitar, but he's cool on the Steely Dan albums)
Lee Ritenour (Also very Kenny G'ish. Avoid his concerts - too poppy and posy, but he's got technique and can write some good tunes).
Leni Stern!*
Lionel Loueke
Luiz Bonfá
Mark Whitfield
Martin Taylor*!! (Often sounds like 2 guitarists in one. Amazing. I am proud to be British with musicians like this around!)
Mick Goodrick*
Mike Outram* (Always doing the rounds here in London)
Mike Stern!!
Niebla, Eduardo*
Nguyên Lê*! (Check out his version of Little Wing!)
Norman Brown (Too much sugary background vocals, but some of his tracks really stand out. Better Days Ahead - nothing to do with Metheny's tune - is an excellent tune even though it is of the smooth jazz kind. Very 'Bensonesque' style even when he sings)
Nuno Ferreira* (Great modal jazz on "long distance calls" on Fresh Sounds label. Portuguese player who plays with New York musicians.)
Osamu Ishida* (Plays on hard-to-find Dogatana with Watanabe)
Paco De Lucia!!*#
Paco Peña*#
Pat Martino!! (Think Tank album is superb. Amazing when he had to learn the guitar all over again).
Pat Metheny!!! (Can't wait for the Mehldau/Metheny date. Both are Iconic players. Note the three exclamation marks. Inventor of several guitars as well. That multi-stringed Picasso guitar and what he gets out of it is awesome)
Paul Bollenback!* (Great playing on Gary Thomas's Seventh Quadrant - a seminal album)
Peter Bernstein
Peter O'Mara* (To be discovered on obscure TOny Lakatos albums)
Phil Upchurch*
Philip Catherine
Ralph Towner
Raphael Rabello
Romero Lubambo!
Roni Ben-Hur
Russell Malone!
Stanley Jordan!!* (Unbelievable tapping style. Can play 2 guitars at once. Discovered on the pavement - sidewalk to you in the USA)
Steve Cardenas
Steve Khan*
Tomatito!*# (Check out his material with Michel Camillo. He brought the house-down with Camillo at the Barbican in London recently. I was there.)
Wayne Krantz* (Can only buy his music, which is great, on
www.waynekrantz.com. Too heavy for some people, though his superb 'Signals' album is more accessible. Also plays on recent Steely Dan albums. When I get to New York again, I hope to find him in the 55 Bar).
Wes Montgomery!
Wolfgang Muthspiel! (A great CD is Mike Holober's Canyon featuring Muthspiel, plus his Bright Size CD is very good and pioneering).