Jerry Goldsmith did some fun stuff in the 80s and 90s, like Explorers, Runaway, Poltergeist, The Secret of NIMN, Total Recall, Gremlins and my personal favorite, The Ghost and the Darkness.
James Horner’s best material in my opinion from the 80s and 90s is Star Trek II: The Wrath of Khan, Krull, Aliens, Willow, Patriot Games and Apollo 13.
It sounds like you’ve got John Williams covered, but I would also suggest Schindler’s List, Superman, Rosewood, Amistad and if you can find the album without the annoying dialogue, Angela’s Ashes.
Adami mentioned Stargate, and the score for the original movie is fantastic, as is David Arnold’s score for Independence Day. Everyone thought he was going to be the next John Williams, with huge Korngold-esque bombast, but he ended up doing lots of different projects.
Danny Elfman has a handful of worthy soundtracks, like Pee Wee’s Big Adventure, Batman, Nightbreed and Edward Scissorhands, which as far as I’m concerned is his best work.
Indescipline mentioned Basil Poledouris, and his Conan scores are indeed awesome. I also like his scores for Robocop and The Hunt for Red October.
Some other random soundtracks that I think are cool, regardless of how the movie is:
Amelie (Yann Tiersen)
The Fountain (Clint Mansell)
Tron (Wendy Carlos)
Interstellar (Hans Zimmer)
Signs (James Newton Howard)
Annihilation (Ben Salisbury and Geoff Barrow)