There are spoilers in all of these, so if you actually intend to watch one of these abominations I'd recommend skipping my description.
Halloween III: The Season of the Witch - Take away Michael Myers and everything that makes Halloween Halloween, then throw in bad actors and a nonsensical story about Halloween masks turning childrens' heads into cockroaches. To top it off, you get to hear the most annoying jingle ever conceived about ten times on TVs in the movie. It ends with the main character yelling "Stop it! Stop it! Stop it! Stop it! Stop it!" into a phone, and by the time the movie was over, I felt exactly the same way he did.
Zombi 3 - I've seen pretty much every zombie movie out there and this one has to be the worst (that says A LOT). Well, actually it's pretty good because it's so unbelievably bad it's hilarious. The story doesn't make any sense at all, the music consists of the same cheesy theme looping the same 4 seconds over and over, and the English dubs don't match what is happening on screen. I love the part where the main characters take shelter in a hotel and happen to find a crate of M16s and Uzis in the basement. It was also pretty great when they run into a military patrol and the main character cocks his revolver, then the entire squad of soldiers simultaneously charge their M16s. But the movie's crowning achievement is when someone opens a fridge and a zombie head inside magically flies about nine feet and bites him in the neck. The director later said this was the part he was most proud of in the movie, because he knew the whole thing sucked terribly.
Fantastic 4: Rise of the Silver Surfer - I don't expect a lot from my in-flight movies, but this one really lowered the bar. They spend the whole movie chasing the Silver Surfer. They capture the Silver Surfer. He says he is a servant of Galactus, the world-eating villain, forced to mark worlds to be devoured in order to save his own planet. Somehow, they convince the Silver Surfer to confront Galactus and save the Earth. So, he just flies up into the big black cloud representing the bad guy and explodes. That's it. The movie's over. After sitting through an utterly boring and poorly written comic book movie, I at least expected a nice epic battle like in Spider Man and X-Men. I never read the comic books, but what kind of hero is the Silver Surfer? He could've saved countless worlds from being destroyed by sacrificing himself, but apparently he likes riding a surfboard through space better than preventing the deaths of trillions.
