To craft a message with the sole purpose of converting people to your own point of view is, technically, propaganda. I don't have a problem with Christian themes being in these works, but propaganda can never be great art. (Is your favorite song a protest song? Or a political slogan?)
Consider the words of Umberto Eco:
"A narrator should not supply interpretations of his work; otherwise he would not have written a novel, which is a vehicle for generating interpretations."
A good piece of art allows for many interpretations. For example, as a child I was shown the story of The Tortoise and the Hare, and I was told that the moral of the story was, "slow and steady wins the race." I disagreed - it was my conviction that the hare would have won if he hadn't gotten cocky, so I learned that one should simply keep their head down and work hard. (I was a very practical 8-year old.) The bullies learned that they shouldn't brag about winning until they actually crossed the finish line. Despite these different interpretations, all of us benefited from the wisdom of the story.
So, we see that even a child's fable can have multiple interpretations, and, as such, the story has a very personal meaning to each of us, because it's a meaning that we teach ourselves.
Can Christians produce these kinds of stories? Can our songs point to God's beauty without being pushy about our agenda? Will people ever watch Christian movies without getting the feeling that they're being manipulated into making a decision? Of course, such artwork may not be what the church wants to see, because allowing multiple interpretations of a story could dilute the intention of it.
If a Christian film tells a story without leading the viewer toward a specific conviction, will it serve a purpose to the church? All I know is that the church couldn't get much less relevant than it is, now, so creating genuine art can only help.