Where are Jethro Tull ? Marillion ? I think Marillion is more representative of neo-prog than Glass Hammer, without prejudging of the latter's talent.
Camel released some very impressive stuff and are one of the few prog-bands, along with King Crimson, not to have headed away from their roots. They belong to one of my favourite prog bands.
Focus released one indispensable record : "The Hamburger concerto" which IMHO is one of the best prog CD ever recorded.
Gong have recorded some very original music in the Allen-era (when Moerlen took the lead, they turn to a plain & simple jazz-fusion band). Fun and serious gathered to bring a unique space-psychedelic mood to their music.
Magma are really unique, blending elements of jazz (Elvin Jones and Coltrane influence), opera, Stockhausen and a language of their own. It is not easy to enter their music but when you get used to it, it is a real delight (especially MDK and Kohntarkosz).
Frank Zappa was influenced by a wide range of music genres (from jazz to rock via contemporaneous classical). Although his music is full of fun, his guitar style annoys me. Nevertheless, I think his live in NYC (1977) is really great.
Genesis remain the standard in symphonic prog. The Gabriel-era is simply stunning. In the Collins-era, there were nevertheless some jewels, like the entire "A trick of the tail".
Pink Floyd were at their best with "Dark side of the moon".
Yes released one really good album : "Close to the edge" ("Going for the one" has also 3 great songs, the others being very low in term of music quality).
With Rush, I have the feeling that Geddy realized a bit late that his voice could annoy people who wanted to listen to their music (their earlier stuff would probably belong to my favourites if the voice was then more mature). That's why I only listen to their eighties records.
Gentle giant are musically excellent but the lead vocalist should have been replaced.
ELP have recorded two essential albums : "Tarkus" and "BSS". I think they were a huge influence on most of the prog italian bands that emerged at the same time.
King Crimson created the perfect mix of hard-rock, prog and classical music. "Red" is the best example of their art.
VDGG belong to the same category as KC but here the saxophone plays the role of the guitar. "H to He/Who am the only one" and "Pawn hearts" are indispensable.
Spock's Beard contributed to the revival of prog at the beginning of the nineties, along with The Flower Kings. Both bands don't play anything original but I always listen to their stuff with a great pleasure.
Dream Theater helped popularize prog in the metal world and contributed to the development of "intelligent" metal. "Images and words" is a must-have for any prog afficionado.
The Alan Parsons Project is a good example of what is called art-rock, a music close to prog but with more simpler structures and accessible to a wider audience.
The Strawbs played folk-prog, but I think Jethro Tull or Renaissance are better examples of what brought this subgenre.
Thanks for having the patience to read my post.