Way to many to list...
These and many others, hold up for me, extremely well for repeated listenings. Although, some of them I don't listen to as often as I used to, since keeping up with new, great music in these genres keeps me plenty busy.
Prog:
King Crimson
Yes - only up to Drama, nothing after is of interest to me.
Genesis - only up to Wind and Wuthering, everything after is unlistenable to me.
PFM - Incredible Italian prog band.
Univers Zero - avant-prog from Belgium.
Gentle Giant
Änglagård - Hybris
Magma - Could be my favorite prog band.
Jazz:
Return to Forever
Mahavishnu Orchestra
Allan Holdsworth
John Coltrane
McCoy Tyner
Steve Coleman
Anthony Braxton
Weather Report
Mary Halvorson
Brand X
Keith Jarrett
The Art Ensemble of Chicago
Classical:
Elliott Carter - Uncompromising avant-garde composer.
The Second Viennese school - i.e., Schoenberg, Berg, Webern
Charles Wuorinen
Joan Tower
Kaija Saariaho
Bruno Maderna
Beat Furrer
Olga Neuwirth
Magnus Lindberg
Gyorgy Ligeti
Miscellaneous:
Frank Zappa - He covers all bases for me, he has music that is classifiable as prog (Inca Roads, as 1 example) , jazz (Big Swifty), classical (Yellow Shark, Perfect Stranger).