Oh boy.
Some great great guitarists have been mentioned, but are we talking technique, melodic ability, over all talent? And in what style, classical, rock, metal, jazz, flamenco?
The all-time best guitarist ever is Paganini, hands down.
Paganini wrote almost all of his violin works on guitar, along with his many guitar pieces. And he sold his soul to the devil long before Jimmy Page did!
Other great guitarists (not in any particular order):
-Andrea Segovia.
-Yngwie Malmsteen.
-Al Di Meola, John McLaughlin & Paco de LucĂa (get this, you'll not regret:
http://en.wikipedia.org/wiki/The_Guitar_Trio).
-Eliot Fisk (Specifically his masterful transposition of Paganini's 24 Caprices for Solo Violin to guitar).
-Brian May (Queen, for the classic rock genre)
The list could go on and on. I, personally, would put Tony Iommi (Sabbath), Angus Young (ACDC), Tom Sholtz (Boston), Alex Lifeson (Rush), and many others on that list, all for their skill, showmanship, creativity, and impact on music. Like I said, the list could go on and on. Even Crosby Stills Nash and Young wrote some awesome folk guitar.
Drummers, did you say?
Neil Peart (Rush)
John Bonham (LZ)
Dave Lombardo (Slayer)
Bill Ward (Sabbath)
Tommy Lee (Motely Crew, yes I said it.)
Vinnie Appice (late Sabbath, Dio)
Andy Newmark (Pink Floyd & Roger Waters - maybe he's just OK, but tripping on acid seeing him play live was life changing).
GAK this list could go on and on also.