When I was a teenager just getting into music I started enjoying all the typical music geek bands like Rush, Yes, King Crimson, and others, though mostly Rush. After a while I started losing interest as got interested in music for other reasons than the shear musicianship of the players.
But over the past couple years (since grad school about 6 years ago) I started listening to Yes and King Crimson again pretty frequently. Yes definitely can take some left turns into Hokey-land from time to time but they also have an amazingly rich musical vision. How many other bands have created an album that is almost symphonic in scope (Fragile) (its about 40 some minutes long and manages to keep reuse themes you hear at the beginning of the album throughout the music. very cool).
King Crimson is just cool, experimental, and edgy, like Bartok (and maybe a little Messaien) on electric instruments. When I was a teen I didn't quite get it. It really helps to have heard some of the 20th century music that so influenced them.
Rush, well, ok, them I can't listen to anymore. Rhythmically interesting but melodically and harmonically they're generally pretty dull. And the lyrics! Ok, Yes can definitely be a little _too_ much with the philosophical bits. But most of it doesn't make enough sense to quibble with. Rush, OTOH, has lyrics that only a 17 year old suburban white geek can appreciate. And I did then, but I just can't now.