Warning, I will be mentioning the endings to several movies. So spoilers will ensue.
We have seen these movies time and time again. Less than 5 minutes into the movie, you know the ending even without knowing more than the basic plot. When I saw the first "Wishmaster" movie, by the end of the opening voiceover, I knew how the movie would end. However, you just can’t believe that these movies would be so predictable. The mere thought of a writer being unable to think of a single original ending should raise your blood pressure. Well, a lot of the typical slasher movies from the 80s and many of the current b-movies seem to be forced to have these ridiculous endings
1. The "is it a dream or not" ending was driven approximately 841 feet into the ground.
Movies have done the "dream ending". Though to be fair to Freddy Krueger, most of his movies have numerous scenes where reality is hard to distinguish at first from the dream world to excuse them from the far lazier movies using the "is it a dream or not" ending. The most famous of the terrible dream endings would be The "dream" ending can always give the shock ending without any logic whatsoever behind the cheap scare. A number of the "Nightmare on Elm Street", "I Know What You Did Last Summer" or "Event Horizon".
2. Time travel movies have to walk a very thin line to keep from logically undoing the entire movie.
The paradox of making sure history isn’t unwritten is hard for the typical moviegoers to follow. If a time traveler from the future tries to change a historic event or stop a future villain from altering some past event, was the event going to happen no matter what? Time travel has a hard time escaping the feel of predetermination or that all the consequences are completely ignorable. When the 2 best explanations of time travel and its consequences are the "Terminator" or the "Star Trek: City on the Edge of Forever" episode, you aren’t going to get very technical explanations of time travel. Every single action continually alters and compounds the number of changes from the original time stream like in "Sound of Thunder" or "Butterfly Effect".
3. The monster drives the hero insane ending.
Yes, the main character has faced the fires of hell and not cracked. However, something incredibly small does cause our hero to snap like a twig. This is more commonly referred to as the HP Lovecraft ending. Why actually having the hero driven insane starts to make the idea of a sequel easier? If the hero then becomes the killer, we get the "Friday the 13th: A New Beginning" version of the ending. How does the hero always seem to get possessed by the monstrous demon at the very end of the movie?
4. The movie that sets up its own sequel.
This is typically the shock ending. The "Wait, we did everything right to stop Freddy, Jason, Santa Claus. How can this be???" ending. The slasher, monster, etc is defeated but still they somehow aren’t 100% dead but just mostly dead. If that isn’t enough, the monster will be killed but it has left a few eggs behind. Can you guess that those eggs always start to look as if they’ll hatch right before the credits start to roll?