I agree with every name listed by everyone...as being a good guitarist, and underrated. I'll add a few more names....Richie Sambora, Vivian Campbell, Mattias Jabs, John Norum...
But my personal choice for most under-rated guitarist is Jake E. Lee...trying to be the guy that replaced Randy Rhodes had to be tough. I thought Ozzys album w/Jake "Bark At The Moon" was very average, but the guitar playing on "The Ultimate Sin" is fantastic, even now.
And Jakes work with Badlands is outstanding...especially their self titled debut...still an awesome record that is not talked about that much.
One more name I'd like to add...and those that know my tastes know I like it heavy, so this may sound strange coming from me, but...Prince can flat out smoke a guitar! And the only way I ever realized this, was seeing his Super Bowl half time performance from a few years back.
He was awesome, and really had a rock-n-roll vibe during that performance. I was surprised and shocked at how he tore it up! He can put a lot of rock players to shame.
Agree with you on Prince. This year is the 25th(!) anniversary of "Purple Rain" yet no special edition CD is coming out as far as I know. Very strange.
agree on the Prince deal. a few years ago when he played the Superbowl, and they had a press conference announcing he would be playing, an announcer got to the podium and said "Prince will now take any questions from the press" and Prince got up with his guitar and proceeded to wail away not allowing any of the press to say a word. Awesome.