I do have to put marcus as easily the best guitarist I've ever heard who doesn't have his own band or album. Even among the other guitar players of the world he ranks really high. Muris and Gabriel as well! All three of you have really inspired me with what you do.
Others would be, Mark Knopfler who has just a perfect style and tone, Eddie Van Halen who can make anything sound amazing, Gary Moore who has some really touching stuff, Gilmour for his perfect phrasing, Billy Corgan, Jonny Greenwood and Ed O'brien for their epic alternative rock solos and spacey numbers etc, Vai, Satch and Gilbert for achieving amazing technique without losing the music, Slash even if only for the classics he's given us, J. Mascis of Dinosaur Jr for having a pretty distinctive virtuoso-grunge kind of style which I find irresistible, Kurt Cobain, Neil Young, John Frusciante, Kelly Jones and Matt Bellamy who all have in common a rather low technique, but amazing rhythmic placement and note choice kind of style. Page, Beck, Hendrix, Clapton and the other 60's-70's blues guitar heroes, Santana and Brian May both have great tone and technique I think, I love their stuff, Kirk Hammett for some really classic stuff I think (even though many would like to disagree), Keith Richards, John Fogerty, Joe Strummer, Buddy Guy and Buddy Holly, Trey Anastasio, Dave Mustaine, I could go on for ever. Can't pick a best