Angus Young is over-rated. He was never considered among the greatest until recently.

Jeff Beck is considred great, and may still be under-rated. One reason: If you think about it, virtually every one of his many instrumentals is basically a solo, start to finish. How many guitarists could pull that off AND still wind up with pieces people would want to listen to.

Michael Gurley (formerly of Dada, now guitarist in The Kiefer Sutherland Band and in his own band) is incredibly under-rated. The band itself deserved much more attention than it received, but listen to his guitarwork on some of their albums, e.g., American Highway Flower. (I'm only familiar with his work in Dada, and saw them live multiple times.)

The guy writes guitar parts that were distinctly original, included solos that involved whatever effects, technique, etc., were needed to fit Dada's songs perfectly, and his guitarwork was always musical (in my book meaning that they were entertaining and sounded good: They left you wanting to hear more.) Check him out.

Dada was an incredibly talented trio: Guitar and vocals (Gurley)r, bass and vocals (Joie Callo and drums and vocals(Phil Leavitt). They are so talented that Callo and Leavitt started their own act (the 7Horse Band), and write and play great rock songs... as a duo! Check them out, too.