What is a Christian movie? "Christian movie" is not a concrete term with an absolute definition. It means different things to different people and in different contexts. I can think of at least five different approaches to defining a Christian movie, four of which are valid, as they look at the movie itself and its content and the fifth definition which is invalid as it looks at the circumstances surrounding the movie and not the actual movie itself.
The first way to define a Christian movie is to ask if it presents or deals with out core evangelical message of accepting Jesus Christ as your personal Lord and Savior or deals with some other explicitly Christian theological teaching. The great French movie Diary of a Country Priest features a story thread of a woman who must forgive God for the death of her son and be reunited to God.
The second way to define a Christian movie is to ask if it promotes our broad values. These are things like love thy neighbor, the golden rule, service to the poor and so on. While these may not be explicitly Christian truths and I understand people's wariness of a watered-down social justice Christianity, these things still fall under the umbrella of Christian truth. Christ Himself speaks of such things in the Gospels. This category can include a whole lot of movies, but ultimately, a lot of movies, even ones we wouldn't think of, are at least a little Christian whether they intended to be or not. Secular society will be hard-pressed to lose its compass entirely. A great example in this category, although it includes some supernatural elements, is It's a Wonderful Life, which deals with George Bailey's service to the working class and the value of every human life.
The third approach is that a movie positively portrays Christianity and Christians. A lot of older Hollywood movies, even when not primarily religious, were at least set against a Christian backdrop. Now, many mainstream movies seem to be going in the opposite direction and inorganically secularizing the worlds they create. One great movie that provides a positive portrayal of a Christian is the Bollywood classic Amar Akbar Anthony. It tells the story of three young brothers who are separated and raised Hindu, Muslim and Christian. Anthony Gonsalves rises to be a positive example of a good Christian.
The fourth of the content-based approaches to Christian movies are Christian allegories. Think of the numerous narratives that contain some sort of Christ-figure. The further we go back in art, the more we realize that everything secular is secretly somehow an allegory for the sacred. So many great stories are Christian allegories. As a less popular example, Superman Returns clearly treats the Man of Steel as a Christ-figure for humanity.
The fifth approach to defining Christian movies is to say a movie made by an officially Christian production company, a church, or made primarily for a Christian audience. This seems to be what contemporary Americans usually mean by the term. While this can be an important category to talk about and I have written about it a number of times, it seems wrong to call these Christian movies because we are defining movies by how they were made or their marketing strategy rather than the movies themselves and their content. Now if they also have Christian content, they can be fairly included. This mindset has led many Christians to miss a lot of great Christian movies that fit the other categories because they are not advertised through the right channels. Facing the Giants, a breakout hit with these audiences, is somewhat of a prototype for the modern Christian film industry.
Ultimately, there may be more ways to define a Christian movie, but these five are a start.