hetfield - best metal rhythm guitar for me. notice his playing, he's more like a rhythm metronome! check his consistency when he plays! next is mustaine on rhythms.
friedman - great heavy all-around player. way better than hammett. can also play other music other than metal.
zakk wylde's pinch harmonics become too "common" in his playing. becoming this as his "trademark" tachinique in playing, but having it too much is not that good, IMO... parang nakakasawa.... but his gigs with ozzy kick ass!!!! iommi got flushed! heheh
hammett gets all the attention, due to metallica's mainstream exposure, but his playing gets sloppier and sloppier at the moment... check out their lisboa gig....or check the rock am ring gig on youtube.... his lead intro on one was off key! and his MOP lead seems to be slower in tempo than the required speed! he also commits "obvious" mistakes!
i dont know but dimebag's tone suits the metal genre... the scooped mids characterisitic in his tone might not appeal to some players but giving some of the mids in might be helpful, i.e. megadeth, some metallica stuff, old sabbath, etc....