For every successful blockbuster and horror film, there is usually some cheaply made knock-off meant to capitalize on the hype. This results in films like Atlantic Rim, Abraham Lincoln VS Zombies, etc. These usually get pushed straight-to-video or dumped onto the SyFy channel.
For every few laughable rip-offs, there are actually one or two that have more effort put into them. They may be unoriginal but at least they can provide decent entertainment or even become classics themselves. In some cases, these are actually rip-offs that managed to get a budget behind them.
Pitch Black
Notorious for being one of the most underrated sci-fi films of the early 2000s, Pitch Black is the film that helped put Vin Diesel on the map. It features a group of people that crash land on an alien planet in the distant future. When the sun goes down, things get bloody and dark.
Vin Diesel's Richard B. Riddick became such a fan-favorite that he received two sequels. The first film itself is clearly inspired by films like Aliens due to the film's main threat known as Bioraptors. This is because Riddick creator David Twohy made Pitch Black off of a manuscript he made for Alien 3 that got rejected.
Orca
Jaws was the first movie to be called a blockbuster and is one of the most iconic movies ever made. So after it came out, there were a lot of knock-offs including Piranha, Tentacles, and even other shark movies. One that became infamous was Orca based on the book of the same name.
Rather than a killer animal randomly killing innocents, Orca is a revenge story. After an orca's mate and child are murdered by a poacher, it goes on a killing spree; killing all that were involved with the poacher. While it's no classic, it has garnered a following due to being a Jaws ripoff with a neat twist.
REC
When The Blair Witch Project hit theaters, it terrified the world so found-footage movies were the new thing. In 2007, a Spanish film known as REC attempted to do the same thing but with a zombie-like threat inside an apartment building while someone films the whole time.
REC would actually become such a hit that it would receive several sequels along with an American remake known as Quarantine. Quarantine was the result of when films like Paranormal Activity really made the found footage subgenre take off.
The Descent
In 2005, there were two movies about people lost in an uncharted cave with monsters. Both came out in the exact same month. One was a big-budget theatrical film called The Cave while the other was an independently made film by Neil Marshall known as The Descent.
While it's difficult to say who ripped off who, it would actually be Neil Marshall's film that would succeed. The Cave quickly fell into obscurity while The Descent would become a cult classic. Simple concept: a group of cave divers enter a cave and become stalked by Gollum-like monsters. It was so scary that its infamy warranted a sequel that was, sadly, not nearly as good.
Intruder
In the 1980s, the slasher genre exploded with so many attempting to do what films like Halloween did so well. One of these was a little slasher with a sprinkle of comedy known as Intruder. Another simple concept: late-night workers at a convenience store are being stalked by a mysterious slasher villain after closing time.
With guest star appearances by Bruce Campbell and Sam Raimi himself, it's clear what kind of movie it is. It's a slasher that has fun with itself while still providing some thrills. Over the years, Intruder has become labeled as an overlooked slasher gem.
DeepStar Six
After James Cameron's The Abyss, the late 1980s surged with several deep-sea horror films. This resulted in films like Leviathan and The Rift but none got quite the following like DeepStar Six. Essentially, it's Ridley Scott's Alien but at the bottom of the ocean with a giant crustacean monster stalking the crew.
The concept while unoriginal, the monster is a unique one for the time and some of the kills are rather memorable. It also attempts to give the characters more depth than your typical slasher fodder. DeepStar Six was not kindly reviewed on release but gained a cult following over the years and even inspire movies like Underwater.
House Of 1000 Corpses
Rob Zombie as a filmmaker is a divisive one due to his jarring, vulgar, and gritty style. People tend to either love or hate his films and that is certainly the case with his directorial debut. House Of 1000 Corpses features a group of people on a road trip; they end up in the middle of nowhere and a strange family holds them hostage for torture and killing.
Sound familiar? That's because House Of 1000 Corpses is very much inspired by The Texas Chainsaw Massacre in almost every way but with some Rob Zombie twists. It did have its fans and as a result, Rob Zombie made a whole trilogy out of the characters.
Dog Soldiers
British soldiers barricade themselves in a small house as bloodthirsty werewolves attempt to break-in. Director Neil Marshall strikes again and he openly admitted to Dog Soldiers taking from Night Of The Living Dead and several other films.
Fortunately, it resulted in Dog Soldiers often being labeled as one of the best werewolf movies ever made. All on a very tiny budget, Dog Soldiers is a great action/horror film that excelled in a time when werewolf movies were starting to fade out.
Friday The 13th
Yes, one of the most successful horror franchises ever made was actually a ripoff at first. From the opening scene of the point of view of a person murdering a teenage girl to many other aspects; the original Friday The 13th was an even lower budget ripoff of Halloween.
Of course, history was made and eleven more films in the franchise were made including a crossover with Nightmare On Elm Street. Pamela Voorhees died while her son Jason took over with many ridiculous but cherished portrayals.
Lake Placid
Take Jaws, put it on a lake, and replace the shark with a crocodile: the result is Lake Placid. A horror/comedy that features a mysterious creature killing in a lake in Maine. It turns out to be a thirty-foot crocodile that brings together the likes of Bill Pullman, Oliver Platt, Bridgett Fonda, and Brendan Gleeson.
With great effects by Stan Winston, a dedicated cast, and a healthy balance of comedy and horror, Lake Placid became quite the sleeper hit and a return for monster films at the time. Sadly, it would get a franchise of terrible sequels for the SyFy channel afterward.