If you don't love the first 10 minutes, why do you sit in your chair for another half hour before you decide to leave the theater? Or why do you stay for the whole thing just to writhe in pain and agony?
I contest that you know by the end of the first sequence if you're going to like the movie or not. The trick is to watch for signs, and realize the signs when you see them.
ALL movies know to establish a genre. Usually when we go to a movie we know what genre the movie falls in, and this is what upsets us about What Dreams May Come. (The previews say it's a, "feel good movie," yet we leave the theater trying to slit our wrists.)
Example. Ace Ventura is a comedy. The first scene consists of Ace dressed as a delivery boy as he kicks around his "fragile" package. It's a comedy and it starts with a laugh.
We should know if we're scared, the movie is a horror film. If we're laughing, there's a chance we're watching a comedy. If we're crying, there's a chance the movie sucks. If the screenwriter has chosen to omit a genre-inspired opening, then there's a good chance you're watching a really bad movie. But, then again, you may like bad movies.
So how do you tell that YOU will personally hate the movie you're watching after the first scene? By asking a few simple questions. At the end of the first scene, (or in some cases sequence,) ask yourself this magic phrase, "Do I care?" (Beware there is a difference between curiosity and care. We are curious to discover how Tom Cruise escapes in the beginning of Mission Impossible 3, but we don't really care if he succeeds.) If you don't care, get up and leave because the movie you are watching SUCKS.