As i know, Japanese Anime Producers really respect the depth and carefulness of what they are going to draw. For example, when drawing a tree, they carefully draw every leafs, every shadow that will contribute to the movement when the tree contacts with the wind and so on. All these details were painted by Artists' hands (Not by those machines or computers that the American usually use). The plot are usually based on the light-novels that are very well-known.
My perception is, since Japan has a hard condition in resources, weather and disasters. So what they put in their movies (or cartoon) will somehow reflect their dreams, their cultures, which make them deeper in compare with other movies.