My vote would've gone to Steve Howe if Gilmour hadn't been on the list. I love his guitar sound, but none of these that I've heard can conjure up the kind of emotion in their guitar playing quite like Gilmour I think. He's distinctive and although his style has been mimicked, he does it best.
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And to generate some discussion, McLaughlin's guitar playing is overrated, I think. He's good of course, but listening to Mahavishnu's Orchestra or the albums he did as part of the guitar trio (with Paco De Lucia and Al Di Meola), I tire of it quickly. Soemtimes, it's so in your face it becomes almost vulgar and annoying I think.
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Here's an example .. Listen to it f.ex after the 1 minute mark :
Is it musical splendor or guitar wankery? I think there is a too big element of wankery in there and I find it somewhat disruptive. Because of this, I prefer Weather Report and Return to Forever over Mahavishnu actually.