guys check out the guitar's hung on the wall. https://www.guitarsatbmusic.com.au/frontrunner_2005/digitech.jpg
i would say it's between joe satriani and paul gilbert.i have seen vids of the two and i find gilbert to be the better instructor.steve vai plays some weird stuff sometimes.
paul gilbert -- album : terrific guitar trip (he is greatest alternate picker i think) genere : metal, hard rock
I havent heard all of em but of whom i've heard n seen, i think i prefer to say Dimebag Darrell is a God, not necessarily to say the greatest. If this is a choice of the greatest then the answer will never be found cos its all bout a person's taste n style of music. A jazz n blues person usually doesnt appreciate Dime & his counterparts & my very own close friend (a metal freak n guitarist) doesnt think much bout Hendrix n others......well this choice doesnt go with everybody, i said only a few prefer it this way.
i would say paul gilbert is the cleanest and fastest sweeper in the world... he can sweep and rake all day and do it with awesome flair and style ..even steve vai and joe sat cant sweep like paul alternatin pickin .-hmmm ..this is very difficult to judge cuz most of the really shred guitarists dont pick in there solos except john ..they all play legato .so..that aint counted .. so fastest alt picker is very difficult to decide . i il say michael angelo batio or yngwie malmsteen