Johnny Thunders (solo, Heartbreakers, & NY Dolls) - Johnny should have been a superstar but ruined it for himself with substance abuse which affected his playing. He was a great songwriter as well.
Kim Mitchell (solo & Max Webster) - Man, this guy is great but he has to be witnessed live to really appreciate his talents. My wife gets bored seeing long solos played live but she always says that she could listen to Kim play all night. I've probably seen him live at least 20 times
Johnny Winter - He's well known as a bluesman but in the 70's when he was rocking out to his blues/rock style he should have been a guitar god. All you have to do is check out his 'Captured' live album or his 'Still Alive & Well' album
Alvin Lee(10 Years After) - for me, the real hero of the Woodstock Movie