Tony Iommi is so great. His riffs are well known but to 100% replicate his style is very difficult. I guess if you know his physical limitations and adjustments to overcome them it puts it into perspective that it is not a normal guitarist you are trying to copy. To me the first 4 (or 5) Sabbath albums have a unique quality pretty much unmatched by anything else. To me they are special. I think these albums have spawned about 4 or 5 subgenres of metal (at least). Regarding Neil Young, I have been searching for the Steve Terreberry break down of Neil Young style guitar playing, but I guess it is gone now. He had a massively accurate mockery of Neil Young's lead guitar style. He has a few tunes I think are cool for sure, but he is an example of someone who is bad on guitar, bad at singing, but somehow is able to write and record a pretty substantial amount of great songs. I mean seriously there are about 1000 far greater guitar players or vocalists I could come up with, yet Young has recorded probably a dozen songs that even as a non-fan I have to admit are pretty good.