If you want to make a successful animation, you could think about the graphics and how smooth the characters look. You could make sure the mouths are in sync with the voices. Make sure the theme of the animation is gripping and think about your audience. An example is Pixar Studios. Their main target audience is children, but their content is still good for all ages. A good idea is to make your content family-friendly, this will make sure you get more watchers.
I hope this could help you...