I like fantasy and comedy, but the plot shouldn’t be too complicated. And now you have to decide what type of cartoon are you making. There is the normal tv show, and the cartoon movies. If you’re into normal tv shows that last around half an hour, the story must be decently paced, there must be a reasonable problems that the main characters have to solve. The characters must all have easy to understand but unique personalities so they can be shown within the little amount of time you have.