In American English, we say "to see a movie" when we view it at a movie theater. For instance, 1. Tonight, I am seeing the new Spider Man movie with my friend Jason. 2. I saw that movie last night at the West Springfield cinemas. 3. I want to see the movie "Jupiter Rising" when it comes out next month. 4. Do you want to go see the new Harry Potter movie with me tonight? We say "to watch" a movie when we view it at home, in particular, on DVD, BlueRay, VHS (if you still have a VCR laying around), NetFlix, Hulu, Youtube, etc. For instance, 1. I watched "X-Men: Days of Future Past" with my girlfriend last night after we had dinner. 2. John came over last night and we watched a few movies on Netflix. 3. Mark is coming over tonight to watch a few movies with me. He really wants to watch "X-Men: Days of Future Past" but I'm not sure if I am up to it. 4. Which movie do you want to watch tonight?

As with the more general uses of these two verbs, 'watch' suggests a more deliberate action. This is why it tends to be used more for watching movies at home, where you have an almost limitless choice of what to watch. However, you can also 'see' a movie at home, particularly if it is part of an evening's broadcasting schedule and you just happen to 'see' it. If you go out to a cinema (GB English) or movie theater (US English) we usually say 'see'. The difference is quite subtle. As for the choice of noun, the distinction is much simpler. ' 'Movie' is the standard term in US English, with 'film' being reserved for technical and academic use. Americans have told me that 'film' sounds pretentious to the US ear. 'Film' is the standard term in British English, although 'movie' is occasionally used for some typically American productions.

"Movie" vs. "film": In the US, we always say "movie" when talking to friends or other people. "Film" is a more technical term, the one you would use in written form, or if you are describing the movie in a more formal conversation. "Watch" and "see" also have different subtle meanings. When you are sitting down in front of the screen (either at home or a the movie theater), you are "watching" a movie. But when you are planning for the weekend, you would say: I would like to "see" a movie (meaning you would like to go to the movies)

watch

Both can be acceptable, it really depends on context to know which one sounds better