This article will tell you the secrets of good animation.
Good animation have more common with theatre than drawing or painting.
It depends mostly on how the character acts.
Take a look at these two pictures:
Can you tell me what the cowboy is doing in the first picture?
Can you tell me what the cowboy is doing in the second picture?
I can't tell you what the cowboy is supposed to do in the first picture. It just looks unnatural.
In the second picture, it's clear that the cowboy is tired (or sneezing). Maybe he's going to bed.
This is the difference between a thinking character and a controlled robot. Your job as an animator is the create the illusion of live. Make the character behave like it's thinking and acting on it's own.
The goal of animation is to make the publicum forget that what they are watching is animated.