Easily Jeff Beck ...
I agree with some of the other choices too, ie. Chuck Berry, Hendrix, SRV, EC, Johnny Winter, D. Gilmour, Zappa, etc. A few of the "new guys" can hold their own as well, ie. J. Lang, Smokin' Joe Bonomassa (sp?), Nate Cavalierre ... Slash has nice tone ... and the young guy in the band Indigenous is showing much potential (although he should stop trying to imitate SRV so closely). Kenny Wayne leaves me cold though ...
But there's a lot being left out - Robert Johnson, Buddy Guy, Luther Allison, Albert King and Freddie King (BB's a great guy, but can't hold a candle to the other "Kings" - BB's main talent is his tone), Peter Green, J. Burton, Scottie Moore, D. Gatton, Neil Y., Santana, Steve Howe, Warren Haynes, Mick Taylor, Keith Richards who practically revolutionized the art of rhythm guitar playing, and almost single-handedly popularized open tuning (RJ was the first modern player to do so, though). Gotta love Keith's 5-string though ... This list of guitarslingers could go on and on ...
But I must violently disagree with a couple choices - #1 -Jimmy Page. JP is no real innovator, and 90% of the time a downright "slop" player. He copped most of his chops from Jeff whilst in the Yardbirds, and shoot, he didn't even come up with the violin bow idea - the father of David McCallum (Illyah in "The Man from U.N.C.L.E.) put the idea to him. #2 is EVH. His playing is largely part Eric Clapton and part Jeff Beck. Can't think of a single, innovative thing he has ever done.