Hi m360p!
Just like any kind of story, how good it is and how many people it reaches, depends of the execution and storytelling.
How the story is told is as important as the message of your story.
An example of good storytelling in a movie based on Christianity is "The prince of Egypt". Is mostly biblically accurate, they manage to make people feel the greatness of God and care about the people of Israel. The visual effects are EPICALLY GLORIOUS and the songs and scenes Will TOUCH YOUR HEART. Is even apreciated by non-christians because of all that.
If your story involve lessons from Christianity, is very important how you approach them. Being preachy is not recommended. (that applies to any story with any kind of lesson from politics, religion or whatever). Remember, you can show what Christianity is and share some lessons too, but you can`t force people to believe in something. The only thing you can do is to do your best to show Christianity in an honest and interesting way.)
Things to be carefull about:
-avoid preachyness (that applies to any political, ethical and religious statement in a story)
-dont guilt trip with hell or anything because that would alienate people
-avoid straw men (making everyone who disagrees with the lessons in your story evil and/or stupid) A deeper definition and examples on this link: https://en.wikipedia.org/wiki/Straw_man
-Avoid Mary Sues/ Mary Suetopias (Making a character or society perfect because they agree with the author or the lessons of the story)
Hope this helps!