While history is full of really interesting stories, the problem with a movie based on something real is that...it has to be more or less based on something real. A good story starts slow, builds to an eventual climax, and then ends dramatically. But what if, in the real story, all the drama takes place in Act 1? What if there are no real antagonists in the second act besides time and natural barriers? What if the ending is a fine pay-off...but not really "wow" enough for a movie. If you're making a movie, there are certainly things you can do to add tension, but in the end, it's going to be obvious you were bound by a true story.
As more and more tragedy films come out (i.e. Patriot's Day, Deepwater Horizon, 9/11, Flight 93, Captain Phillips, Sully, etc), I feel as though we're getting more and more "true stories" closer and closer to when they actually happen. While that sounds fun...we may find our storytelling becomes limited to just truth.