I feel as though Up is a umber one film because it is just amazing quality. The characters are defined, the plot is well crafted and the movie just expresses what Pixar is all about. The movie begins with an amazing montage of the main character's life, how he got to be who he is today and the moments in his life that define his character, and then continues to slowly unravel the rest of the story. You can't help but fall in love with the characters and you begin to find yourself at the edge of your seat as the plot thickens; you root for the characters all the way.
The creative process that animators, writers, and film makers underwent is clearly showcased in the film and shows why this film is a winner of multiple Academy Awards. This is a must see.