Up to and including the 2005 remake, there have been 9 Amityville films — some being TV-movies or released direct to video:

• The Amityville Horror — released July 27, 1979 to 748 theaters
  opening weekend $7,843,467 • US domestic gross $86,432,000
• Amityville II: The Possession — released Sept 24, 1982 to 1,200 theaters
  US domestic gross $12,534,817
• Amityville 3D — released Nov 18, 1983 to 1,254 theaters
  US domestic gross $6,333,135
  aka Amityville III: The Demon or Amityville: The Demon
• Amityville: The Evil Escapes (TV-movie) — broadcast May 12, 1989 on NBC
  aka Amityville IV: The Evil Escapes
• The Amityville Curse (direct to video) — released May 7, 1990
• Amityville 1992: It's About Time (direct to video) — released July 16, 1992
• Amityville: A New Generation (direct to video) — released Sept 29, 1993
• Amityville: Dollhouse (direct to video) — released Feb 18, 1997
• The Amityville Horror (2005 version) — released April 15, 2005 to 3,323 theaters
  opening weekend $23,507,007 • US domestic gross $65,233,369

Jay Anson sold the film rights to CBS. American International Pictures bought the rights from CBS and informed the Lutzes that they were going to turn their story into a film. The Lutzes informed them that they held 2/3 of the copyright, and it wasn't solely Anson's to sell. During the negotiations, the Lutzes didn't receive very much money, but they got the sequel rights, which is a very rare thing to get.

No, the original film used a house in Tom's River, NJ. The real house in Amityville was not used as a filming location for any of the films.

No. Grammy-award-winning composer Lalo Schifrin wrote a beautiful score for The Exorcist, but unfortunately it was not what director William Friedkin was looking for, so it was not used. Instead Friedkin chose Mike Oldfield's hauntingly hypnotic piece Tubular Bells, released by the new Virgin label a year earlier. You can hear Schifrin's original Exorcist score on some copies of the Exorcist soundtrack.

According to Schifrin, "Many people thought The Amityville Horror was the same music I wrote for The Exorcist, but that's not the case, obviously. It's one of the first scores in which I used children's voices. It had a really nice effect."

No, the 2005 "remake" contains many new fictional elements and serious distortions of events regarding both the DeFeo family tragedy and the Lutz family haunting. It should be viewed as a piece of Hollywood fiction and nothing more.

To date, the original book by Jay Anson remains the most faithful account of the Lutz family's experiences in Amityville, while Gerard Sullivan's High Hopes is recommended reading for those interested in the DeFeo murders.

source: The Amityville Horror (book), 1977; The Amityville Horror (film), 1979; The Amityville Horror (film), 2005; Focus Newspaper Online website, 2005; High Hopes (book), 1981