hmmm... I dont know what to say here... Zak? yeah he's good, but you cant call him the best gutiarist.. cos there's no such thing... And Iommie, you gotta respect the guy, he was the innovator (and LEFTY!!! i tried to win his guitar, cos i wanted a lefy SG... but that's a whole different story)...
I think you need to broaden your horizons, cos you'll see there's no such thing as "best guitarist"... cos it's about style and feeling... it's not like some boring mundane tast that you can be assesed on... I mean I like Hendrix more than most guitarist, but that doesn't mean he's the best... or his song are ALL better than any ther guitarists..
I'm no fan or via, but that doesn't mean he's crap at all...