Yes, "The Amityville Horror" is based on a true story. The film is inspired by the real-life events that occurred in a house located at 112 Ocean Avenue in Amityville, New York. In 1974, Ronald DeFeo Jr. murdered six members of his family there. A year later, George and Kathy Lutz moved into the house and reported experiencing a series of paranormal phenomena, which they claimed were linked to the murders. Their experiences were later detailed in a book by Jay Anson, which led to the film adaptations. However, the authenticity of the Lutzes' claims remains controversial.

The "Amityville Horror" franchise includes several adaptations, but the most notable are the 1979 original and the 2005 remake. Many consider the 1979 film scarier due to its atmospheric tension, slower build-up, and classic horror elements that evoke a sense of dread. The 2005 version, while more graphic and featuring modern special effects, focuses more on jump scares and less on psychological horror. Ultimately, which is scarier can depend on personal taste—some prefer the haunting subtleties of the original, while others may find the remake more intense.

While "The Amityville Horror" is often cited as one of the classic horror films, the title of the "#1 scariest movie ever" is subjective and varies among audiences. Many lists and polls frequently mention "The Exorcist" (1973) as the scariest film due to its disturbing themes and intense atmosphere. Other contenders include "Hereditary," "Psycho," and "The Shining." Ultimately, what is considered the scariest movie can differ based on personal experiences and fears.

There are numerous "Amityville Horror" movies due to the enduring fascination with the real-life events surrounding the Amityville house, where a gruesome murder took place in 1974, followed by claims of paranormal activity by the Lutz family. The original 1979 film's success sparked a franchise, leading to sequels, remakes, and spin-offs. The story's blend of horror, true crime, and supernatural elements has inspired filmmakers to explore different aspects of the narrative, resulting in a variety of interpretations over the years.