Finding Nemo was a cartoon that basically looked like any other cartoon that took place on dry land. You could substitute birds or airplanes for fish and you'd get the same feel.
No one knows how well the Avatar sequels will do. What made the first Avatar a hit was the groundbreaking 3D effects and the light show of CGI aspect of it. People had never
seen anything quite like that before. The story itself was pretty weak and just a retread of any number of noble savage westerns of decades before. By now 3D and fantastic GCI
are been there, done that.