God, there are so many great solos from so many under rated, under appreciated and unknown artists, hard to know where to start. But I will start with some better known ones, Steely dan has had some good ones, very early Chicago in the 60s, Green grass and high tides by The Outlaws. Frank Zappa and everything done in Hot Rats (my god!), Blue sky by the allman bros, some of the work by Michael Karoli from CAN is incredible, magic man by heart.
There were some crazy good solos from a...Danish? Dutch band? from the 70s called Focus. I know I heard a good solo from this guy called Buckethead once, can not find it now. Eternal wheel by Ozric Tentacles.
I tend to not like things like Stevie Vai, just to...soulless.
Will think of more later. edit: Rory Gallagher is criminally overlooked, from the early 70s. Steve Hillage, especially 60s and first half of the 70s is another criminally under rated, amazing guitarist in so much that he did.