1) Terminator. His best by far
2) Aliens. Just...great. Especially the Director's Cut.
3) Terminator 2. I'm an 80's/90's baby, and you can't live then without having quoted this movie ad nauseum. It's a classic.
4) The Abyss. I've never seen it, which makes it better than the last 2.
5) Titanic. I really do NOT like this movie, but it has a topless scene in it, which bumps it above the last place film on the list. The second VHS of this film is amazing (yes, I'm old), as watching death and destruction is cool, but man...move over Rose. Ugh.
6) Avatar. I probably missed out not seeing this film in the theater and watching it at home. From a story standpoint, it does NOTHING new, and the characters are very forgettable. Also...unobtanium. I just...can't forgive that one.
In all fairness to Cameron, none of these are BAD movies. So...respect.