Man, so many dittos, so little space.
I must first speak the word: Gilmour.
Anything he does is my favorite solo ever. However, I'll direct your attention to The Final Cut for some of his best and least-known gems.
And though it's only been heard by post-Gilmour Roger Waters fans such as myself, you HAVE to check out Jeff Beck's myriad solo breaks in What God Wants from Amused to Death. DAMN, but that boy can play.
I'm glad someone (Buck, I think) mentioned Michael Gurley's solo on Dada's Dorina. That whole album, Puzzle, has some really great guitar playing on it. Not sure what happened after that, though a friend of mine saw them at Stubbs in Austin a few years ago and said Gurley tore the roof off the joint. I can believe it.
Ditto on Crossroads. Damn.
And hey, nobody be dissing the solo on Stairway. That's some seriously good stuff.
I'll throw out one that I don't think has been mentioned, and will definitely earn me some dork points, but: Peter Frampton, Do You Feel Like I Do.
Look, I don't even like Frampton most of the time, but you gotta have your ears missing to not hear the ass-whipping being laid down there. Though it's become a cliche now, I can see why that album flew off the shelves.
Okay, must stop now before I get going...