Ok... this is my personal list (obviously)... but...
Don't hold the sequels against this. It's just perfect and it has the best ending of a movie ever. And the action sequences still get my blood pumping.
And Agent Smith? Is there a better villain?
Memorable quote: "Mr. Anderson..."
2. Star Trek II
Watching Shatner and Montalban attempt to out-ham each other is one of the most glorious sights you will ever see. And no FX looks as good as the ILM models. CGI is great and can do a lot more in terms of ship movement and camera moves, and I understand that it allows TV shows, like DS9 to do awesome, big battles you could not do with models.
But the models in ST II and the Star Wars movies have such a real feel to them that CGI can't (yet) replace.
Memorable quote: "KHANNNNNNNNNNNNNNNNNNNNN!!!!!!!!!!!!!!!!!!!!!"
3. Empire Strikes Back
This is the movie that made the Empire seem menacing, made it seem cool. Darth Vader is the star of this movie hands down, with the best supporting puppet nod going to Yoda. A Lawrence of Arabia like trek from the frozen wastes to the swamp to the clouds... the best Star Wars movie ever.
Memorable quote: "I'm not afraid." Yoda "You will be"
4. Planet of the Apes (the original- don't get me started on the remake)
Charlton Heston is god. Maybe not THE god but A god. And in this movie his gravitas makes something that should be absurd (and is at times) have a nightmarish, through the looking glass quality when it could just be funny (like the later movies).
Memorable quote: "You did it. You finally did it. Damn you. Damn you all to hell!!!!!!!!!!"
5. 12 Monkeys
Weird and absurdly funny in a very twisted Terry Gilliam-esque way. Bruce Willis and Brad Pitt both turn in fantastic performances, you're on the edge of your seat wondering how it's going to work out until the final frame, and there's so many subtle nuances it begs to be watched again.
The best time travel movie. Ever.
Memorable quote: "What are you THEN, huh? Consumers!"