First and foremost, it’s the story which makes a movie good. Does the story make sense? Is it believable? Even if it is sci-fi, is it believable within the context of the world they have created? Is it logical?
Second, can you get lost in the movie? For 90 minutes or two hours do you feel like you have been whisked away to some other place? Are you getting to witness another place and or time as a silent observer? When the movie is over do you feel like you are transported back into the theater seat (or couch)?
Thirdly, the acting must be believable. Do the people feel like they are real? Are they moving and talking like they would in real life? A great actor is one in which you never for a second think that they are acting.
Fourth is style and setting. It is my belief that these aren’t as important as the first three because a good movie can literally just be a still camera shooting the action and dialogue. It can be black & white. As long as what is happening feels real, is interesting and makes sense. But when the film has a certain style and a great setting it is definitely a bonus (see Drive -2011). Too much style can be poison though. Too much fake shaky-camera work can be overly distracting (see any of the early Bourne movies.
Fifth is editing. Editing is so important. Is the film bloated? Is there a three hour movie that should have been cut to two? Do the cuts make sense? Do you feel like they smash you into the next scene or does the transition feel natural? Sometimes the director or producers won’t allow an editor to do the right thing. Films like The Last Samurai or There Will be Blood, where the entire last act should have been trimmed come to mind. These are good movies that would have been even better had they been cut down. Some of Tarantino’s most recent works feel bloviated. Hateful Eight & Django Unchained come to mind. And if he lopped off the silly killing Hitler sequence in Inglorious Basterds and carving letters into Nazi’s foreheads at the end, the movie probably would have been taken more seriously. Trim the fat. Get rid of the superfluous.
My favorite movie, Apocalypse Now was best in its original theatrical Release version. They have since added back deleted scenes and re-released it as “Redux”. Those added scenes really knock that movie down and I refuse to even acknowledge them. There is a part in “Hearts of Darkness: The Making of Apocalypse Now” documentary where F.F. Coppola gets really angry at “The French Scene” and yells that the scene is being cut from the movie and that no one is ever to speak of the French scene again. Well guess what? He was right. It’s terrible. And guess what else? They added it back to the movie in the “Redux”. F.F. Coppola is one of, if not the greatest film director in history, yet he hasn’t produced anything good in decades. He lost his edge. His hunger. He has gotten so bad that he is even ruining masterpieces from his early career, like the aforementioned Redux debacle. Godfather III was awful. And even his offspring are making garbage. Lost in Translation was unwatchable in my opinion.
Some movies are being filmed as they are actually finishing writing the story. Die Hard is one of these movies. And though this is usually a recipe for disaster, that movie ended up being very good. The sequels are pretty bad however.
Music isn’t as important to me. It can really add to the movie or it can distract somewhat but it definitely does not make or break the movie. Some people felt the soundtrack to Interstellar was terrible and distracted from the film. I can honestly say that a movie score has never ruined a good movie. There are actually bad movies with fantastic soundtracks, Hannibal (2001) for instance. But it didn’t help it in the ratings department. That movie sucked.
Basically, if you have a great story, believable actors and a decent editor, you can make a good film.