As time passes, this list gradually evolves and moves around a bit. This is my list as of April 24, 2019.

Pulse (Pink Floyd)
Aqualung (Jethro Tull)
Emerson, Lake, & Palmer (ELP)
Aja (Steely Dan)
Tarkus (ELP)
The Division Bell (Pink Floyd)
Led Zeppelin II (Led Zeppelin)
Led Zeppelin IV (Led Zeppelin)
Fragile (Yes)
Trilogy (ELP)
Chicago 9 (Chicago)
Minstrel in the Gallery (Jethro Tull)
Romantic Warrior (Return to Forever)
Physical Graffiti (Led Zeppelin)
Madman Across the Water (Elton John)
Goodbye Yellow Brick Road (Elton John)
Electric Ladyland (Jimi Hendrix)
Elegant Gypsy (Al DiMeola)
Abbey Road (The Beatles)
Friday Night in San Franciso (Paco de Lucia, Al DiMeola, John McLaughlin)
Close to the Edge (Yes)
Blood Sweat & Tears (Blood Sweat & Tears)
Heavy Weather (Weather Report)
Brain Salad Surgery (ELP)
Thick as a Brick (Jethro Tull)
Houses of the Holy (Led Zeppelin)
Blind Faith (Blind Faith)
The Doors (The Doors)
Led Zeppelin III (Led Zeppelin)
John Barleycorn Must Die (Traffic)
The White Album (The Beatles)
Led Zeppelin I (Led Zeppelin)
Machine Head (Deep Purple)
Works Volume 1 (ELP)
Selling England by the Pound (Genesis)
The Six Wives of Henry VIII (Rick Wakeman)

Please post your list or other comments below.