Don't agree - without Jimmy Hendrix guitar as we know it would not have evolved to the level that it has. Almost every guitar legend from the 70's up was influenced by Hendrix. Jimmy Page was also a great player who could probably do with a bit more of a mention. As far as over rated goes I would have to say Angus Young - even though he is a great player and his riffs are very catchy I don't believe he shoud ever feature in the top 100 lists of all time.
Underated for me would have to be Shawn Lane - I have always heard of him and only recently stumbled across a vid of him on youtube and was completely blown away. I've never seen anything played as fast or as complicated or as unique - plus he was around in the 70's and early 80's - leagues ahwead of his time. Vai, Satch, Petrucci etc have all cited him as one of the best players of all time and as a major influence. I read an interesting quote (I think from Petrucci) "When the modern guitar gods want lessons they go to the music of Shawn Lane" - he was simply THAT good (he died a few years ago unfortunately...).