I agree. While I don't think my two favorites are solo pieces, even after all these years I truly love to hear....
Roundabout by Yes
Suite Judy Blue Eyes by CSN and Y (I'm not sure about Young)
The opening to "Roundabout"(even though I've heard it and heard it and HEARD it) sets the stage for an unforgettable musical ride. My favorite Yes song-please don't make me pick one,I'm so torn.
As far as guitar riffs,who hasn't played air guitar to "Smoke On The Water"'s opening riff?
Great song. One of the most soothing tunes you'll ever hear on a "rock & roll" radio station.