most usually if a novel or a movie falls flat, it's because the author/writers/director lost track of the story arc. Some basic points:
1. Almost always, a satisfying story has three basic elements: conflict, crisis and resolution of the conflict. This is true of stories on a screen or stage or on a page. Think of: Romeo & Juliet, Terminator, Moby Dick, Emma, Clueless, A Thousand Acres, Master and Commander.
2. Good, balanced, healthy people in happy situations are sweet, but boring. You want to be related to them, but you do not want them populating the only novel you've got to keep you busy on an eight hour flight.
A problem (conflict) is what makes a story. There's always SOMETHING in conflict. Two people fall in love, BUT their families object... he's black and she's white...she's old and he's young....she's got a PhD and he's got grease under his fingernails...she's married...she's democrat and he's libertarian...he's a professional violinist and she's Deaf.
3. The conflict can be between people, or not. Sometimes conflicts are completely inside one person's understanding of themselves. (It looks like the conflict is between Sue and this granddaddy of a trout that has been eluding her for so long, but it's really about.... her inability to let go of relationships that are over; her lack of faith in herself; the doubts she has about going to shipbuilding school). But sometimes a person or persons will be in conflict with a place, or the idea of a place. Other conflicts might be: A man and a machine; a woman and a horse; a town and a river. A conflict can be very obvious and in-your-face (he loves her but she loves somebody else) or very subtle (can he face the truth about himself?). But almost always, the conflict ON THE SURFACE is masking some larger conflict. "I want you to pay my parking ticket" might really be "I want you to accept responsibility for me and everything I am." "You never take out the garbage" might be "I'm angry at you for messing up my life and I'm going to make you pay."
4.
It might not look on the surface to be the case, but they do. The power passes back and forth, and this is how tension is created, and you keep the reader interested. A woman incapacitated in a wheel chair, unable to feed herself, hardly able to talk, can be a poweful presence in the life of a young, healthy daughter. Power takes many forms.
With those points in mind, have a look at this simple schematic of how tension and story arc work together is adapted from Janet Burroway's classic text on writing fiction, now in its sixth edition (click on the image to enlarge). If you study it, you'll see how power moves back and forth between the forces of good (Cinderella) and evil (the Stepmother). Kinda like capture the flag, but without the flag.
You can take any novel or movie or play or episode of television and look at it in these terms to figure out how it's structured (or where the narrative begins to lose its rhythm).
One of the movies I sometimes use when I teach this stuff (specifically because it is seriously flawed) is Notting Hill. If you think through the points above and try to fit that movie into this schematic, you'll see where it goes wrong.
An important point: sometimes a novel or a movie goes wrong, but you forgive it because some other element you truly admire (the acting, the cinematography, something) convinces you to overlook the flaw. But the flaw is still there, and figuring it out will help you with your own writing.