This depends on what you mean by worst. Worst as in technical playing ability, like accuracy and speed, tone and touch or in terms of composing? For example, somebody like a Steve Vai or Malmsteen are fantastic players in terms of their mastery of certain techniques but I would much rather listen to Stevie Ray Vaughan or David Gilmour as they are "better" guitarists in my opinion.
Gilmour is the best example of a debate like this. On a technical scale he was nowhere near Malmsteen's level but he had much better touch and tone and was capable of composing much better guitar based music.
I do agree about The Edge though. He is a one trick pony, making a multi-million dollar career out of the delay pedal...
