I can easily accept Hendrix for the top spot because of the enormous impact he had. Just ask a certain David Gilmour who his greatest influence was.
Same goes for Clapton. He was, after all, God in his Cream days.

It has to be a tough call. Very subjective task. And they, again, enlisted the help of many, respectable guitarists and musicians and producers, just to show how difficult it is to leave so many off the list.