I'll give another vote for some old-school Metallica: One, Master of Puppets, Fade to Black, etc etc. There are so many great ones.
Freebird is far and away my favorite solo. Gary's and Collins' dueling is just so awesome.
No More Tears by Ozzy has a short but sweet solo in it.
Cliffs of Dover by Eric Johnson is a 5 minute solo

Quite possibly the best guitar work I've ever heard. Its so precise and controlled.
Dream Theater has some awesome solos as well. Petrucci is an incredible guitarist. (Although Portnoy is better at what he does IMO) Some good songs from them include The Glass Prison, Fatal Tragedy, and also search for John Petrucci's 8 minute solo on Kazaa or something. Simply astounding.