Are films part of literature?
Absolutely! Screen plays are written works for specific audiences with specific issues to present. Film is the universal communication tool using images and music to convey ideas. Reviewers of films study the actors, the lighting, the music, the plot lines, the pace and delivery and write reviews about them. There are different genres in film, just as in books. Short films, documentaries, horror, mystery, drama, comedy, etc.
Literature effects cultures and defines characteristics of certain peoples...film does the same thing. While I never encourage just the watching of a film as opposed to reading the original text (sometimes films are original in themselves--the screenplay is the original and worthy of study), film is worthy of study and classes have been created with the title of "Film as Literature".
Wikipedia defines "film" as:
"Films are cultural artifacts created by specific cultures, which reflect those cultures, and, in turn, affect them. Film is considered to be an important art form, a source of popular entertainment and a powerful method for educating — or indoctrinating — citizens."