Also, other overrated guitarists include: Eric Clapton, Eddie Van Halen (most overrated guitarist ever), Ace Frehley, Angus Young, and Kurt Cobain (I like Nirvana, but come on, he was no guitar whiz)
Underrated: Randy Rhoads, James Hetfield, Dimebag Darrel, Kerry King, Jeff Hanneman, and (on a less heavy side) Jesse Cook, whose amazing accuracy and mastery of technique along with his style variety ranging from flamenco to classical amazes me.
Rhoads was a great musician, Hetfield is the driving musical force of Metallica and a great player who is sometimes overshadowed by Kirk Hammett's popuarity, and Pantera and Slayer may not be the most musical bands in the traditional sense, but they still have talent.