The Edge. The band's overrated, but he's amazing.
Most overrated is Hendrix. Only because when you're that good, people are likely to exaggerate.
Jon Gomm is pretty damn good.
Dimebag, John Petrucci, Nuno Bettencourt, Alex Lifeson, and some others I've forgotten
EDIT: ****, I just remembered Rory Gallagher, by far the most underrated ever. Interestingly, Hendrix was (allegedly) asked what it was like to be the greatest guitarist in the world, to which he replied "I dunno, ask Rory Gallagher".
Stevie Ray Vaughn - he's not under-rated by the people who know him but he is the best guitarist of all time IMO and doesn't get nearly the amount of hype that hendrix etc. do (in the UK at least).
Hey, Hendrix is my favourite guitarist. The emotions he could conjure from a guitar were unimaginable.
In terms of recognition from his peers, he certainly has the largest following. Almost to an extent where people wish to distance themselves from him, because so many have tried to emulate his style and failed.
I should also note that although I liked SRV, he really is just the guitarist that came closest to imitating Hendrix, if he were alive I'm sure he would say Hendrix was miles ahead of anyone, perhaps ever. I really don't like comparing musicians in those terms, but when it comes to Hendrix, he just epitomises originality.
a truly amazing guitarist is jose feliciano . jus amazin , theres a video somewhere on youtube of him playing flight of the bumblebee
Brian Setzer is incredible.