One of the main problems that faithfilms have had is that they've been written in a way that would only appeal to Christians. Even successful "Christian" films haven't had much of an impact--financially,critically, or intellectually--outside of the Christian market. On the other -based hand, some religious or culturally motivated films from other groups have managed to cross over into the mainstream, films like Bend It Like Beckham, The Namesake, Big Fat Greek Wedding, or on a large scale, films like Schindler's List or The Last Samurai.
One thing that has kept Christian-themed films from breaking out has been a simple lack of quality. There are exceptions, of course, but even most defenders of the Christian film community would agree that there hasn't been much to crow about on the artistic scale.
But assuming for a moment that a high quality script could be written (and several have been, such as The Mission, Chariots of Fire, The Apostle, etc.), I believe there are five key issues that should be considered when attempting to create Christian-themed storylines and characters that would be accessible and compelling to a mainstream audience.
1. Show Christians with flaws. Many Christian-themed scripts present too rosy of a picture of the Christian experience. Oftentimes, whatever flaws that are presented are surface-level and quickly overcome or resolved. Unfortunately, that's not realistic, nor is it even an accurate portrayal of the Christian message, which is that we are all deeply flawed human being who are in constant need of grace. In fact, we would (or at least should) acknowledge that most of our biggest flaws are never fully overcome.
Of course, it's true that the overwhelming majority of Christians portrayed in mainstream films are usually the most flawed or crazy characters in the story, so there should be a balance. But faith-based films often go too far in the other direction.
2. Have self-deprecating humor. One of the great things about movies like Greek Wedding and Bend it Like Beckham is that they were willing to poke fun at some of the traditions and idiosyncrosies of their respective cultures and faiths. And they didn't do it harshly or with cynicism. The fact is, every people group has its own silliness, and far too often Christians seem to be unwilling to have a sense of humor about theirs. An audience member is far more willing to suspend his cynicism or wariness if he senses that the storyteller doesn't take himself too seriously.
3. Not every problem has to be solved by a Christian. In real life, many non-Christians are just as kind, generous, and truthful, if not more, as any Christian you'll meet. In many Christian-themed films, there are few non-Christian characters, even fewer who don't end up converting, and even fewer who help solve problems. It can be a turn-off to a non-believing audience member if he sees that in the world of the filmmaker, Christians are the only ones who have the answers or solutions. Think of Schindler's List and Greek Wedding--outsiders to the faith were oftentimes heroic or wise.
4. Show reality. This is similar to point #1, but I'm not referring to personality traits here. I'm referring to the fact that life is often dark and hard and difficult, and answers don't come quickly or easily, and solutions don't always arrive. If you look at the Old Testament, you'd see a grim and disturbing picture of life, and not everything wrapped up nice and neat. Too often Christian-themed films want to sugarcoat the human experience in order to maintain a G or PG rating. But the most important part of the gospel story is the fact that sin and evil exist, and that God doesn't always make life on earth a smooth ride. I believe that non-Christians would be more open-minded to a Christian-themed film if they thought it actually represented their life experience in some way, and not just the happy or clean parts.
5. Not every story has to end in a salvation experience. Many Christians think that a film isn't a Christian film unless it shows a conversion or includes the explicit gospel message. But think of the parables Jesus told, or most of the stories in the Old Testament--many of them were simple life lessons, or cautionary tales, or simply historical records. There are many fascinating and exciting stories from the Christian experience that don't necessarily involve an actual spiritual conversation, and that doesn't make the stories any less "Christian."
Hollywood studios are right now seeking faith-based entertainment to tap into a marketplace and business opportunity they never thought existed. Writers and filmmakers who are Christians need to be ready, and they need to be able to tell stories that can have wide appeal so that the studio will be incentivized to make even more films like it. And even more important, films like this can have the intellectual and spiritual impact on society that Christians want so badly to have.