Oops, completely missed that post. Obviously I agree with the sentiment.
Definately do not think Brian May is under-rated.He is a Rock Legend.Well deserved
Ani DiFranco– although she’s best known as a songwriter, singer, and indie rebel, her acoustic lead picking underneath her lyrics is incredible.
I’m a firm believer in acoustic lead playing as the touchstone for great guitarists, and Ani’s skill at that is amazing. All the more so because she doesn’t highlight it, but just blends it into the songs.
SECONDED. I picked up a ‘best of’ CD called “Big Guns” as a sort of overview of his work and was just blown away.
My other picks:
Vivian Campbell [check out his blues CD “Two Sides of If”]
Brian May
Alex Lifeson
Michael Hedges
No one would ever know the name!
I nominate Bob Smith. Plays like Robert Johnson and Slash, with some Steve Howe and Hendrix style thrown in. Only plays in his garage, late at night when the kids have gone to bed, drinking homebrew beer and in a rocking chair his wife bought at the Salvation Army.
What? Nobody knows of him? I guess I win…
David Gilmour (Pink Floyd)
As with May, I hardly think Gilmour is “underrated”. He’s quite possibly my favourite guitarist, but come on, his solos in “Comfortably Numb” alone are legendary.
I’m not a musician, so I was wondering if Adam Jones (Tool) counted as an underrated rock guitarist. Or do you all see him getting the props he deserves, or does he not deserve them, from a musician’s perspective?
He grew up in the same town as Tom Morello – they went to high school together in Libertyville, IL, and I can see in their sounds how they’ve both influenced each other. Yet, both are distinctive and contribute significantly to defining the sound for their respective bands.
If he’s not an underrated rock guitarist, then I would definitely nominate him as one of the most underrated visual artists I can think of. Him and Alex Gray, with whom he works on Tool album art. Jones did win a Grammy for the last Tool album package art (which was the coolest CD art I’ve ever seen).
Musicians, what say ye?
ETA: Oh, I see Rolling Stone rated him as #75 in the Top 100. Also, speaking of Morello… did you know he’s a graduate of Harvard? I just saw that on his Wiki page. Who knew?
Jones is respected - but in kind of the same way as Keith Richards and Pete Townshend - as a Bossman rhythm guitarist who drives the song, not as a gunslinger. His use of a Silverburst Les Paul has brought them back in vogue with reissues and an increase in the originals’ collectibility (heavy bastards tho they are ;)).
Tom Morello was at Harvard when a friend I used to drum with went there - they used to compete in Battle of the Band contests, etc. He says Morello was a spandex hair metal guy - in which case more power to him for making the change!
[Completely pointless nit that shows how superficial I am]
I love Morello’s playing, his innovative use of effects, his attempts to engage on an intellectual and political level even when I don’t agree with his positions - but, dude, do you have to strap your guitar up so freakin’ high - what, is there a flood coming?? You don’t have to be Jimmy Page or Johnny Ramone, but can it at least cover your belt buckle? ‘sall I’m askin’!!
;)
[/Completely pointless nit that shows how superficial I am]
Bruce Cockburn doesn’t shred very much but I was surprised to find out that the solo in “If I Had a Rocket Launcher” was by him and not some hired gun. He does a lot of great guitar work mostly in the background.
I have no idea of how he’s thought of. I assume he’s a legend in Canada. 
What bout elsewhere?
I came here to mention Chuck Garvey and Al Schneier from moe. as well. Simply amazing guitarists.
He had a couple of hits in the 80’s - Lovers in a Dangerous Time, Rocket Launcher, etc. - but didn’t really maintain a big rep after that. No clue about his guitar skills.
I have heard of moe. but never heard them - and I don’t have 36 minutes for a video at work ;). I have heard that they are both jam-bandy and can be harder-edged - I like the harder part, but have limited tolerance for a lot of jam-bandy stuff (Allman Brothers / Derek Trucks is about where I will go in that space) - any specific tracks I should listen to?
moe. can defintely be considerd a jam band. That being said, they do have a more rock and roll sensibility and do not always noodle self-indulgently through a song for fifteen minutes or more.
Some of my faves are: Akimbo, High and Low, Kyles Song and The Road. Also, there’s a nice acoustic version of Bluejeans Pizza on youtube that I like a lot.
Cool - I will check them out; thanks.
I haven’t got much time today, (and you probably won’t be able to watch this at work, anyhoo) but check out this two minute clip about Bruce Cockburn. There seems to be more, but I’ll look the rest up later.
You are NEVER allowed to see me play standing up! 
I want that 24th fret somewhere between my left nipple and my heart, so I always know where to find it. I suspect many metalheads have a different geophysical marker…
How about Tak Matsumoto from B’z?
I am not a metalhead, but as a meat-and-potatoes rhythm guitarist, if the guitar doesn’t cover my boys, I can’t rawk to my fullest! 
You jazzy/classical types actually have to care about wrist angles and such - I have no issue with that. But our boy Tom is laying down some gorgeously sinewy funk-based metal - you’d think he’d need his guitar lower to feel the groove more…but that is just silly nitpicking on my part…
I’ll throw in a vote for Mark Knopfler; plenty of respect among guitarists (and #27 on the Rolling Stone list), but ought to be a household name.
Underrated, but probably not the most underrated.
Tak is someone I have not heard but is discussed regularly on guitar boards. I am pretty sure he is a Les Paul nut and posts on the LP Forum - I think Gibson came out with a Custom Shop Tak model…
As for Knopfler - look, I am all for any excuse to shout out his name, but underrated? No way - he is a household name to most folks I know…