I would have to say, from personal opinion, that it would be Eric Clapton, his influence is close to insurmountable. I also love the fact that no matter what style of music he plays, he always stays true to his Blues roots, which is a factor in his ability to reinvent any sound and make it his own.
Jimi Hendrix is good, but i wouldn't say he's the best.
I take that back, Hendrix is better. And I am not saying this just to dispute that quoted statement. Gametesta, no offense, but Kurt Cobain? I can see Chuck Berry, but Cobain? His guitar playing is nothing special. Hell, I have Kurt Cobain's playing skills. If you listen to Nirvana's songs, you'll notice that most of the guitar playing is simple power chords and regular chords.
It's a close match between Paul Gilbert and Michael Angelo Batio, but if I had to choose I would probably choose Paul Gilbert, since he created an amazing guitar, and he's one of the greatest shredders ever.