Why is it that nobody knows anything? William Goldman couldn't have been more correct when he said it, but why was he so right?
I am a business and marketing information addcit. Been doing it since I was 13 years old. Read Positioning when I was 15 years old. I have been marketing myself and other businesses, large and small, on three continents for years. I have even assembled business and marketing plans for movies and production studios. Many others, way smarter and more experienced than I, have been doing it even longer. So how come nobody knows anything yet?
Because: Art is not repeatable. That's why.
Oh, a nicely-assembled marketing binder will give you the impression that it is, but don't be fooled. They'll say this new movie has all the same winning elements as the latest Oscar-winner, or mega-blockbuster, and therefore, is guaranteed (pretty much) to be a success.
Past performance is no indication of future results.
Science is, by definition, repeatable. Everything else is a guess. Wall Street types call it speculation. In Vegas, baby, they call it gambling. But every piece of art is unique in some way. Any movie (whether or not you consider it art) is different from any other movie: the director, stars, writer, producers, crew, budget, effects, storyline, locations, marketing, timeline, release date, and process of making the movie may all be different. Sometimes only one or two elements seem different. But there are always differences, and they are not easily isolated, or repeatable differences.
Movies are not creations that you can assemble or dissect on a lab counter and run through a spectragraph, even though there are many books, workshops, and studio executives who believe that you can. Movies are unknown, risky ventures. There is absolutely no way that you can know in advance if your movie will succeed; you can only speculate- take the risk.
The very best thing you can do is to make what you believe in your heart and soul to be a good movie, and do your best to get it seen by as many people, as quickly as possible, so that it builds a rolling buzz, which hopefully snowballs into a "sleeper", which snowballs into a cult hit, which snowballs into a must-see, which snowballs into critical darling, which snowballs into a commercials success, which hopefully rolls the last mile into an Oscar winner.
Many people will tell you what is a good movie, and why yours is not. Absorb what is useful, but trust your instincts, stick to your guns.
After all, nobody knows anything.