Those lists are always a crock, can't take them seriously. I'm a huge Nirvana fan but Cobain was no great guitarist. I would rank him slightly higher than Joan Jett
I haven't seen someone mentioned that I think is way underrated.
Jeff Healy.
Don't think he's put out anything in years, but c'mon, the guys been blind since he was like 4 years old, plays with the guitar laying flat on his lap and he's better than half the people on those lists. Don't think he's good? Listen to Can You See The Light.