WAY too many great ones, among many subgenres to decide on just a few.
So, I will break it down by subgenre.
Also, let me state from the get go, that I am always saddened to see lists like these on various forums, with the complete lack of Italian bands listed. IMO, some of the best prog ever, came from Italy.
Classic prog:
Yes - toss up between Close to the Edge or Relayer, side 1
King Crimson - Lark’s Tongue in Aspic side 1, but this is close to a toss up with side 2
PFM - Per un Amico side 1
Banco del Mutuo Soccorso - Io Sono Nato Libero side 1
Genesis - Selling England side 1
Canterbury:
National Health - Of Queues and Cures side 1
Hatfield and the North - The Rotters Club side 2
Picchio dal Pozzo - S/T side 2 by a hair
Zeuhl:
Magma - Köhntarkösz Anteria it was released on CD, so there are no sides
Eskaton - 4 Visions side 1
Setna - Guerison CD only, no sides
Koenji Hyakkei - Viva Koenji Cd only, no sides
Avant-prog:
Thinking Plague - In Extremis CD only, no sides
Univers Zero - Uzed side 2
Art Zoyd - Berlin side 1
Henry Cow - Western Culture, side 2
Samla Mammas Manna - Måltid, side 1
Prog-metal:
Pain of Salvation - Remedy Lane, CD only, no sides
The Contortionist - Language, CD only
Wolverine - The Window’s Purpose, CD only
I could name quite a few more per subgenre, and even though I did list mostly recordings from the 70’s, I could name quite a few bands from the last couple of decades that I believe are close to those of the 70’s.
Bands like: Anglagard (Sweden), Deus Ex Machina (Italy), Echolyn (USA), All Traps on Earth (Sweden), Aranis (Belgium), Il Tempio Delle Clessidre (Italy), and quite a few more have recordings that I place near the best.