The best alternatives to Storyline are Chime, HiFiveStories, and Wheel. If these 3 options don't work for you, we've listed a few more alternatives below.
What do you think of Storyline?
AssemblyAI— Speech-to-Text API with superhuman accuracy
Vixeo is an awesome new App that allows you to create movies with Augmented Reality Characters and elements while you direct them with a neat joystick feature! Add animations on the fly and share with your friends!! Who needs a Green Screen to mix Real People with CGI Characters when you have an App like this one!? :D