It's a common question in the world of writing. Just how believable/realistic should this entertainment stuff be?
If a writer's story is to be completely believable, then he or she should make certain that the characters are ordinary people with ordinary struggles. They should spend most of their time concerned with the minutia of life, coping with everyday frustrations. And if their trouble is of a life-or-death nature, we might find that they would die. Such is realism.
The characters in a totally realistic novel will have to confront a real world where life isn't fair and there's little or no justice and endings are messy and often bleak. Those same characters should have dreams, but rarely would they act on those dreams. They should want to be courageous, but they won't usually take the risks associated with courage. Only the rarest individual would ever do anything truly heroic. And almost never would a character undergo a complete character transformation, i.e., as when the Cowardly Lion finds he has courage or the Tin Man discovers he really does have a heart. A worthy dream, but not realistic.
Oh, wait. That's not entertainment fiction. There's a name for stories like that. It's called Literary Fiction.
Literary fiction has great value for what it can teach us about life, and we worship great literary writers.
But the whole point of entertainment fiction is, well, entertainment. We read it to experience characters facing larger-than-life trouble and who respond to that with heroic behavior. Entertainment fiction sweeps us away into a world that we can only imagine because we've never actually had those experiences in real life. Or, if we've had a personal taste of such grand stories, they rarely turned out so well that telling them would make readers come back for more again and again.
In entertainment fiction, readers demand that the stories turn out well, that the hero wins and the bad guy gets his punishment. In a detective murder mystery, the detective must catch the killer. In a romance, the right boy has to end up with the right girl. In a thriller, the special ops team must save the world from apocalypse.
For suspension of disbelief, readers require only that they "buy into the story." The mechanism for that is determined by the story itself. Once we get to know James Bond, we would be appalled if he could suddenly fly like Superman, but we certainly expect that Bond can take on a dozen bad guys in succession. Similarly, we would be taken aback if Superman could suddenly tell the vintage of a glass of wine or know the inner workings of a secret Russian terrorist group. But we aren't at all surprised when Superman can lift a train off the tracks.
Readers' demands for larger-than-life stories require that even if the protagonist in a mystery is a meek, little old antiquarian bookseller, she nevertheless takes risks more appropriate to Jason Bourne than a real-life book shop owner. The requirements of entertainment fiction mean that the little boy who regularly gets picked on eventually finds the strength and courage to teach the bullies a lesson. The underdog basketball team with second-hand sneakers simply must overcome all the odds and take the national championship. The family that is tormented by spirits in a haunted house horror story must, in the end, finally vanquish the ghosts. Realistic like real life? No. But satisfying? Yes, oh so satisfying.
In a completely realistic novel, if a lone teen-aged girl is lost on the ocean in a leaky rowboat, she will drift for a few days and eventually die. But in entertainment fiction, that same girl will learn to catch fish with her shoelaces and navigate by starlight and dismantle one of the wooden seats to use as a paddle in order to find her way back home.
Entertainment stories take us out of our ordinary lives by giving us thrills and chills and a view into a world where dreams come true and there's always justice at the end.
Are they completely realistic? No. That's why we read them.