It's personal opinion. The word best is subjective, and some people may interpret it to mean the best technically, the fastest, the best at writing catchy songs, etc.
There are many different categories of 'best.'
I think Tom Morello is the best. He's well versed in most techniques, and uses them well, he's unique, and he's insanely creative. He may not be the fastest or the best in technique, but he does make a guitar sound good, and in the end, that's what really matters, isn't it?
Yeah, blash and SOAdrox are right what I really meant was who were the best technically, at writing songs, at making a good tune etc...
Who were best in pples opinions!
john petrucci... for the crazy riffs and solos
kirk hammett... for the crazy solos and thrashy riffs
buckethead... for random funny shit and crazy solos + weird riffs