Images and sound are the two most important parts of animation. They are two primary keys to opening the mind, and also the two most powerful senses your mind uses to interpret reality. A whole animation can thrive on a musical score without voice acting, nor does it need any script or story. To say that voice acting and scripts are the two most important parts of animation is unbelievably stupid. They're elements to a genre or style of animation, but are FAR from required. Admittedly they are often overlooked, especially when done well, but that does not justify them as being the most important aspects.
JT1
I agree that voiceover is the most overlooked part of animation. I think that the second is script writing. They are probably the two most important parts as well. You do a good job with both.