That's a lot of childhood movie nostalgia you have missed out on, but even better now becaus eyou can get the full grasp of the messages and plot that they had which as a kid you'd have glossed over anyway only focusing on the gory action and cheesy lines back then
As for 80s/90s scifi...
Goonies
The Thing
Flight of the Navigator
E.T.
Predator
Blade Runner
Alien (all of then)
Batteries Not Included
Inner Space
Short Circuit
Gremlins
2001 Space Odyssey (ok not quite the same era but still a marvel)
FLash Gordon
Masters of the Universe (He-Man)
Sphere
Ghostbusters
Teenage Mutant Ninja Turtles
The Fly
Total Recall
The Matrix
Demolition Man
Equilibrium
Fifth Element
Contact
Cube
Clockwork Orange
Galaxy Quest (parody of Star Wars, very good)
The Abyss
Back to the Future trilogy
Species
Event Horizon
Starship Troopers
That will last a while.