for the untrained ear, for the diletante music enthusiast, it sounds arbitrary and subjective to claim that there is such a thing as the best rock guitar solo of all time.

He will understandably appeal to naive platitudes ("beauty is in the eye of the beholder", etc.), or point to analogs of rankings that are clearly subjective, incomplete, and unfair. For example, the best rock guitar player of all time, where pretty much every list out there has Eric Clapton as the 2nd best and Jimi Hendrix as the greatest of all time.

We will never know if Hendrix reigns at the top because of his talent or because he died young. (Some people go as a far as to claim that Hendrix is one of three musicians who reinvented the way an instrument is played: Charlie Parker (saxo), Thelonius Monk (piano), Jimi Hendrix (guitar)... but early in the 20th century, it was one Charlie Christian who pioneered using the guitar as a lead instrument.)

I digress.

Back to the point. Don't forget the wisdom of John Keats when he writes "beauty is truth, truth beauty".

It's an absolute.

There are extraordinary solos, like the ones in Bohemian Rhapsody (Brian May), November Rain and Sweet Child O' Mine (Slash), Stairway to Heaven (Jimmy Page), and others...

... but above them all...

...from another dimension, the empirical proof that beauty is truth comes from David Gilmour performing the two solos of Comfortably Numb.

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PS1: For the geeks, what gear did Gilmour use? a black Strat, with a bridge pickup DiMarzio FS-1, connected through a Hiwatt DR103, with the Electro-Harmonix Ram's Head Big Muff

PS2: For the non-believers and heretics, here is Rick Beato showing support with his Top 20 Rock Guitar Solos Of All Time.