Of course, listening to native speakers use conversational English in movies is a good way to learn the language. It is not the only way, but it is part of a good curriculum that focuses on all the aspects of a language. Students should also practice speaking and writing to supplement their course.
I'm Dutch and I learned English from when I was 6 by watching TV and movies(we have subtitles, that is the way I learned to associate the words) When our school got to the point where they started to teach English, I already knew all of it.
When I got to the first class of high school, I already knew all the grammar and did not ever have to learn for any test, and would get a 9 easily.
Yes, in my views, it is good to watch English movies because it provides a center where one can understand words correctly and with right expressions. It is better for those who are not from English background as they could also learn correct accent of speaking. In starting, one may face some problems in catching right words but slowly they can get it.