To give credit where credits due, Jimmy Page, Lou Reed, Jeff Beck, Mike Bloomfield and a handful of others had been experimenting with distortion, feedback, volume and other effects before Hendrix burst onto the international scene with his LP "Are You Experienced?" in 1967. But Jimi combined all these and more causing a serious re-evaluation by all guitar players on the scene, forever changing the way that the guitar would be approached. His influence has reached further into the musical psyche than anyone ever has before or since.
It can and has been argued, ad nauseum, that he wasn't really that good of a player, that there are others faster, cleaner,etc. This may or may not be. It is a matter of personal taste and to argue it is a moot point. What is undeniable though, is the fact that no one else has been so widely copied,admired, covered and name checked by so many different guitar players from so many different points in the musical spectrum. From Rock to Reggae, Punk to Funk, Hillbilly to Hip Hop, Heavy Metal to Jazz his influence shines through to this day.
I'm not trying to convince anyone here that he is the best guitarist of all time (he isn't even MY favorite, I'm kinda partial to Earl Hooker, Ira from Yo La Tengo, Lou Reed, Hubert Sumlin and Johnny Guitar Watson as far as favorites go) and I'm not trying to take away any accomplishment from the many talented players past or present. I'm just hoping to show, with some degree of clarity and conviction, that Hendrix's influence has been felt by more people, in more disparate genres than anyone else has up to this point in time.