What makes a compelling film?

I am by no means an expert on film. I'm just a guy who likes to watch movies. Like most people, I've watched good movies, not so good movies, and some downright awful ones. I'll even admit to occasionally indulging my less critical side and watching some of those campy monster movies that they show on the SyFy channel. But even though I can enjoy movies that you wouldn't find anywhere near the Academy Awards, I still feel like I am a pretty good judge of what qualifies for a really "good" movie. I can't put my finger on any one thing that makes a movie good, obviously you can have two movies that are both great, but that are completely different. A good example of this would be my all time favorite movies, The Lord of the Rings trilogy, and another of my favorites, Fight Club. These are two films with almost nothing in common, yet they are both very compelling movies. There is no one thing that makes a movie great, it is a combination of everything that goes into a movie. If a movie has great music but a lousy story, it's going to be a lousy movie; and the best director in the world isn't worth much if no one in the movie can act. A compelling movie is a complex machine, all of the parts need to be working.  These movies are great because all of the pieces worked perfectly together, from writing to acting to directing to editing.