I don't know. I'm not sure there is any one "best guitarist" in the world. Maybe Guthrie Govan, or Joe Bonamassa, or Andy McKee, or Yngwie Malmsteen; or maybe none of the above. I have my personal favorites, to be sure, but whether any of them is "the best," who am I to say?
How in the world could anyone meaningfully measure and realistically compare the ability and skill, the artistry and creativity, the versatility, virtuosity and value of Antoine Dufour and Christopher Parkening with that of Gus G and Synester Gates, with that of Brad Paisley and Keith Urban, with that of Paul Gilbert and Joe Satriani, with that of Al Di Meola and Phil Keaggy, with that of Zac Brown and Zakk Wylde, with that of Jack White and the Edge, with that of Jeff Beck and Eric Clapton, with that of Slash and Mark Tremonti, with that of John Petrucci and Steve Lukather, with that of Orianthi and Steve Vai, with that of Carlos Santana and Michael Angelo Batio, with that of George Lynch and Mark Knopfler, with that of Kirk Hammet and James Hetfield, Glen Tipton and K.K. Downing?
How does one evaluate and quantify the "bestness" of living guitarists like Eddie Van Halen and Jimmy Page, who were surely among the greatest in their heyday, but who haven't contributed much in many years, especially as compared to the likes of B.B. King and Tony Iommi? And where does one situate Jimi Hendrix and Randy Rhoads in the hierarchy of the guitar, when they've been dead these past many years, and yet their music is still being enjoyed all over the world?
If there were any one "best guitarist" in the world, I suspect that he (or she) is probably a session player in Nashville, New York, Houston or Los Angeles, inconspicuously if not anonymously making the stars in the limelight sound good. Or, maybe "the best guitarist in the world" only plays for himself, for the love of the music, and for the pleasure of his family and friends. Perhaps such personal joy and the generous entertainment of local neighbors are further aspects of "bestness" that we should be hard-pressed to calculate, or even to discern.
It occurs to me that, what is true when it comes to the guitarists of the world, is likewise applicable to the whole broad spectrum of talents and trades with which people all over the world are variously occupied. The "best of the best" are not necessarily those who manage to make a name and trunkloads of money for themselves, but are more likely those who quietly go about their tasks in faithfulness and love, simply doing what they have been given to do. In any event, life isn't a competition — those who attempt to make it so, lose. "Greatness" in the Kingdom of God, which is where the only true and real life is lived, is found in the humility of repentance and the confidence of faith; it is not "compared" from one citizen to the next, but measured solely in relation to the Cross of Christ, who pours out His "greatness" for us, and upon us, in Self-sacrificing love. Wherever such genuine greatness is poured out in love for the neighbor, whether by the playing of guitar, or by whatever task is taken up in faith, there is the sweetness of a life that is being lived well.