I agree with ThompsonPen in that the right kind of movie could definitely change your life. Certain movies have absolutely brilliant polts, acting, themes and so forth, as well as important messages.
They can open your mind to new ways of thinking and possibly get you to believe in things you never would have. Some movies can also be truley inspiring. Some movies can make you think twice about your current situation. For instance, after viewing the hardships of others, you may not feel so sorry for yourself.
I would say that there have been several movies that have made an impact on my life, the way i think, and the beliefs I have. I can't think of all of them but some of the films would include The Life of David Gale, The Lovely Bones, Schindler's List, and Philadelphia. Not the best list but what I can come up with at the moment :)