This film is of the same class as "Secondhand Lions" and "Bliss": Namely an epic, feelgood "yarn" depicting character and making numerous small points about life. Indeed, it is a story worthy of Peter Carey.
However, Big Fish is more than a simple feelgood film filled with eccentric events. It is about the "truth" of tall tales, and how some things have value even if they are not true. It has also a lot of classic storytelling elements; for instance, the doctor who is (miraculously) present at both the birth and death of our protagonist, plays the part in this film that is played by the fool in Shakespeare: He is the wise character who knows already the answers to the issues with which the other characters grapple.
In plot terms, it is the story of a man trying to get to know his dying father. All his life he has been told these tall tales by his father. He has heard them so often he is heartily sick of them, and he takes the impression of the storytelling father with which he is left as a mask, a fake front that hides the real person. All he wants is to know what his Dad is really like. Of course, for entertainment reasons the stories all turn out to have a true core, so you never really know where truth ends and fantasy starts (though it might be safe to assume that he was in the army, but that Danny DeVito's character is not a werewolf). Nevertheless, the message in the tales is representative of the father, and in the end the son understands. Also for entertainment, there is a great deal of cross-linking and coincidence, a tool that has been used in films of the last couple of decades with increasing efectiveness (see e.g., "Love Actually" or "Back to the Future").
The death scene is particularly poignent, a death as worthy as one that delivers you at once to Valhalla.
The theme is that you do not need truth to convey message.
The cast is excellent: Albert Finney, Ewan McGregor, Helen Bonham Carter, Danny DeVito, Jessica Lange, and so on. No acting letdowns. The effects, such as they are, are also neat and powerful. The Korean twins are particularly clever, though Kay said that when they are in the distance the animation is visible as such.
This film is definitely an 8 out of 10, and it would be a 10 if there were not so many sound works of the same genre that have gone before.
http://www.imdb.com/title/tt0319061/