Cartoon characters with appeal form a connection with their audience. Character appeal can mean the difference between an engaged audience or a bored and otherwise distracted, disconnected one. In both live action and animated films, the viewer will care about an appealing character as opposed to one they don't give a hoot about. Want your audience to care about the story you are about to tell? Think about ways they can connected with the character. When was the last time you cared about what happened in a story that featured a main character which lacked appeal?
It's hard to invest your time and energy and emotion into a story whose main character is dull and uninteresting. Think about the cartoon characters you find most appealing and interesting. Mickey Mouse is appealing - but so is WALL-E - and they are worlds apart in terms of design and style of animation, yet both are extremely appealing. What is it about them that intrigues you? What story elements that are contained in their very being fascinate you? Is it because the clever use of exaggeration makes their expression fun to watch? Is it their outerwear? Is it their pose - the way they hold their hands or tilt their head?