The best ever solo?
Might be the solo in "Have you heard about my baby" in the John Mayall and the Bluesbreakers with Eric Clapton just tearing the place apart.
Another Clapton great, the closing solo on the song, White Room is way up there in air with the greatest.

Or could be any number of licks traded by Jerry Miller of Moby Grape, playing with Mike Bloomfield on a little known jam album, Grape Jam. There's some incredible stuff put down in that record, enough to send chills down your spine!

Santana and Trey Anastasio have their moments, too.
Or a little known cat named Roger Heath, who I'm sure is somewhere out there, blowing some people's minds.