I have a friend who, for reasons I won't go into, will remain nameless. He and I often discuss blogging, in particular, how and when to be honest in a blog. His sense is that a blog is a place to express yourself, which means to reveal yourself, which means to tell the "truth." My sense is that a blog is a place to express yourself, which means to be honest, which may or may not involve telling the "truth" and which will only be revealing in a secondary manner. His blog is full of descriptions of feelings; my blog is full of movie and music reviews.
Big Fish is a movie about a man who tells stories. The relationship of those stories to "reality" is never clearly explained in the film, but my guess is the movie wants us to appreciate that the stories are honest, whether or not they are "real." The storyteller, played by Albert Finney, is honestly explaining his life when he relates his fantastic anecdotes, and until you can see that, you are blind to truth.
At the film's end, the storyteller's son, who has resisted the fables all his life, finally embraces the art of storytelling and becomes a complete man. I don't know that I buy this ... like the storyteller, I have a tendency to reveal myself through my stories rather than through straightforward expressions of my real feelings, but I also believe more in the concrete world than in the world of fantasy.
The problem with Big Fish, and it's a big one, is that the fabulous tales that are told are often boring (albeit nice to look at) and invariably pointless (is that the point?), which means sitting through the movie isn't quite the transcendent experience it might seem from the previews. You may think you're about to spend two hours with the Brothers Grimm, but once Finney starts blathering, you realize that instead you're stuck for two hours with an insufferable, self-absorbed blowhard.