Your argument comes off as bitter, and really invalid. You're comparing Finding Nemo, which has always been a Disney property, to Marvel, which loaned it's rights to Universal to use as an island in a theme park.
Theme Parks make about rougly 10-15% percent of a company's revenue. Disney did not buy Marvel just to spite Universal for a small fraction of revenue. They looked at the movies, cartoons, toys, games, and comics before they looked at theme park possiblities.
As JungleSkip said, this all just seems as an excuse to pit the 2 companies for the sake of a "battle".