Big Hero 6 is a Pixar film in the best sense. It is every bit as well written, character driven, and overflowing with charm as Toy Story or Wall-E.
This is more a story about a boy and his robot then anything else - probably making the film closer to Brad Birds "The Iron Giant" in some ways rather then the "Incredibles" which is its most obvious comparison.
So say Big Hero 6 is a superhero story is to say ToyStory is about Toys betting up a kid that tortures them.
Its not that its not true, its just that a damns the film by what it leaving out everything important.
Big Hero 6 is a story fundamentally about coping with loss, and its a solid running theme over the movie.
Its one of the heaviest themes you can do, in fact, and it treats it with respect and focus - without making the movie heavy or depressing. Its a clever trick and it pulls it off very well.
And when it does enter superhero specific areas of storytelling, it pulls them of superbly as well. Because it understands that the best comic books in this are are science fiction stories. Its not about punching villains, its about showcasing neat ideas. Posing "what ifs".
We live in a golden age of superhero movies right now because so many writers have realised this. Its obviously not as important as solid character motivations, and plots that make sense.....but it IS the reason you should be doing
a superhero movie at all rather then telling it in a different genre. Its because you have ideas to show of, preferable new ones.
So, if your looking for something with emotional resonance and consistent themes, or if your looking for neat science fiction....Big Hero 6 is both. All wrapped up in a beautiful package of animation which has character and personality coming just as much from expressions and gestures as it is speech.