Funnily, Koyaanisqatsi ranks on the lower end for me for Glass works (no pun intended). I’m a huge Glass fan(atic perhaps), and much prefer stuff like Truman Sleeps, Mishima, Jane soundtrack, Glassworks, Symphony #4 Heroes (Glass/Bowie/Eno), Mad Rush, etc etc. His music composed specifically for the piano is gorgeous.
Amy Dickson’s saxophone interpretations of his violin concertos are absolutely riveting, example: https://youtu.be/ZdUWPA_AX6o