Name some good horror movies that are based on true events/stories?

Psycho (1960)

The character Norman Bates was inspired by Ed Gein, a Wisconsin man who was arrested in 1957 for committing two murders and digging up the corpses of countless other women who reminded him of his dead mother. He skinned the bodies to make lamp shades, socks and a "woman suit" in hopes of becoming a woman. He was found to be insane and spent the rest of his life in a mental institution.

The Exorcist (1973)

William Peter Blatty, screenwriter and author of the novel The Exorcist, was inspired by an article he read in college at Georgetown University about an exorcism performed on a 13-year-old boy in Mount Rainier, Maryland in 1949. The story's details have been muddled through the years -- perhaps intentionally so, in order to protect the family -- but the boy's actual home lay in Cottage City, Maryland, and the exorcism was performed in St. Louis. Evidence points to the boy's behavior not being nearly as outrageous or supernatural as was portrayed in the film.

Jaws (1975)

Screenwriter and novelist Peter Benchley was inspired in part by a series of shark attacks that plagued the New Jersey shore in 1916. Over a 12-day period in July of that year, five people were attacked, four of whom died. A seven-foot-long great white shark was killed on July 14, and its stomach was found to contain human remains. To this day, there is a debate over whether or not that shark was the culprit -- some scientists argue that it was probably a bull shark -- but no further attacks were reported that summer after it was killed.

Audrey Rose (1977)

Frank De Felitta was inspired to write the novel -- and later the movie script -- after he heard his six-year-old son, Raymond, who'd never taken piano lessons, playing music perfectly on the family piano. De Felitta consulted a Los Angeles occultist, who called Raymond's talent as an "incarnation leak," explaining that the boy had lived many lifetimes. The incident led to the author's personal belief in reincarnation.

The Hills Have Eyes (1977)

The movie was inspired by the legend of Alexander "Sawney" Bean, a Scottsman of the 15th or 16th century who reportedly headed a 40-person clan that killed and ate over 1,000 people, living in caves for 25 years before being caught and put to death. His life has inspired numerous stories and films worldwide, including The Hills Have Eyes and the British film Raw Meat, but most serious historians today don't believe that Bean ever existed.

The Amityville Horror (1979) or remak

Perhaps the most notorious horror movie "based on a true story," the film is based on a self-proclaimed nonfiction book describing what George and Kathy Lutz experienced during their four weeks in the house, including disembodied voices, cold spots, demonic imagery, inverted crucifixes and walls "bleeding" green slime. Most, if not all, of the events portrayed in both the book and the movie have been called into question by investigators, and it is widely believed that the entire incident was a hoax.

Most horror movies claiming to be based on true stories or true events are either a gimmick to lure people to see the movie or are loosley based on something completley different.

There are no lot of horror movies based on true stories

Albert Fish

Megan Is Missing

The Entity

The Rite

No One Killed Jessica

Captifs

The Mill

Salo 120 Days

Elizabeth

Rosemary's Baby

The Shining

Amitiville Horror

The Omen

The Wicker Man

Texas Chainsaw Massacre

The Hills Have Eyes

12 YEARS A SLAVE