Too many to list, but I can't put this down without explanation. Sorry.
Aliens. Best of the Alien series. Seriously? No CG critters at the time, and it looked that good?
To Have and Have Not. Lauren Bacall. Smoulder. End of line. As Humphrey Bogart goes, I'll be a heretic and say I prefer this to Casablanca.
Memento. Kept my brain engaged all the way through. Not your typical movie.
Psycho. Put the horror in "horror movie" and changed film-making forever, in several ways.
LA Confidential. Gripping twisting plot, wonderful acting, immersion in the period. Not a perfect movie, nothing is, but it was darn close.
Lord of the Rings Trilogy. Sure, call me a willing participant, just part of the masses. It was wonderfully done - especially the first one.
Silverado. Takes all the Western cliches (minus the Indians, which is okay by me) and does them up right. Great, likable cast.
Terminator, Terminator 2, Jurassic Park, Shawshank, Green Mile, the Bourne series. All great flicks that I can watch just anytime.
And finally, go ahead and snort, but....
Star Wars. You youngsters just don't understand because it's just one more slopped-together and, in revisions, over-edited film. But when it came out in the original form, it was truly, truly, groundbreaking. There had been nothing else like it before, and it was a quantum shift in how movies were made. Grandma and I saw it four times in the first month it was out. It was just that stunning for its time.