The first. Everything else is lazy imitation feeding a dimwitted audience that wants familiarity, not quality.
Now that I have vented, I will admit Aliens was as good as Alien (Alien 3 was a shameful failure). Godfather II can be considered part of a single masterpiece with The Godfather. (Godfather III was a shameful failure). Terminator II was good.
In the Star Wars series ,nothing will ever, ever, ever beat seeing the original on the big screen when I was 14 years old, not knowing what to expect, and having the star destroyer fill the screen and go on and on and on at the beginning. Easily my favorite moment of all time as a moviegoer.