Question: Which unfinished film by Orson wells is based on the film that he claims was the best he had ever made ?  

Context paragraphs:
The Merchant of Venice (1969 film): The Merchant of Venice is a 1969 drama short film directed by Orson Welles based on William Shakespeare's play of the same name.  While actually completed, it is frequently cited as an unfinished film, though better described as a partially lost film due to the loss of film elements.

It's All True: Based on an Unfinished Film by Orson Welles: It's All True: Based on an Unfinished Film by Orson Welles

The Trial (1962 film): The Trial (1962) is a film directed by Orson Welles, who also wrote the screenplay based on the novel of the same name by Franz Kafka.  Filmed in Europe, Welles stated immediately after completing the film: ""The Trial" is the best film I have ever made".  The film begins with Welles narrating Kafka's parable "Before the Law" to pinscreen scenes created by the artist Alexandre Alexeieff.  Anthony Perkins stars as Josef K., a bureaucrat who is accused of a never-specified crime, and Jeanne Moreau, Romy Schneider, and Elsa Martinelli play women who become involved in various ways in Josef's trial and life.  Welles plays the Advocate, Josef's lawyer and the film's principal antagonist.

Moby Dick (unfinished film): Moby Dick is an unfinished film by Orson Welles, filmed in 1971.  It is not to be confused with the incomplete (and now lost) 1955 film Welles made of his meta-play "Moby Dick—Rehearsed", or with Moby Dick (1956 film), in which Welles played a supporting role.

The Deep (unfinished film): The Deep is an unfinished film directed by Orson Welles, based on Charles Williams' novel "Dead Calm" (1963), which was later adapted as an eponymous 1989 film.  Welles produced and wrote "The Deep", as well as played the role of Russ Brewer opposite Jeanne Moreau and Laurence Harvey.

Filming The Trial: Filming 'The Trial' is an unfinished making-of film by Orson Welles, made in 1981, which focuses on the production of his 1962 film "The Trial".

Too Much Johnson: Too Much Johnson is a 1938 American silent comedy film written and directed by Orson Welles.  An unfinished film component of a stage production, the film was made three years before Welles directed "Citizen Kane", but it was never publicly screened.  The film was shot to be integrated into Welles's Mercury Theatre stage presentation of William Gillette's 1894 comedy, but the motion picture sequences could not be shown due to the absence of projection facilities at the venue, the Stony Creek Theatre in Connecticut.  The resulting plot confusion reportedly contributed to the stage production's failure.

Don Quixote (unfinished film): Don Quixote is an unfinished film project produced, written and directed by Orson Welles.  Principal photography took place between 1957 and 1969.  Test footage was filmed as early as 1955, second-unit photography was done as late as 1972, and Welles was working on the film intermittently until his death in 1985.  The film was eventually edited by Jesús Franco and was released in 1992.  It did not include all the footage shot for the film and received mixed reviews.

Ava Lazar: Ava Lazar is an American actress most notable for her role as the first Santana Andrade in NBC's soap opera "Santa Barbara".  She has been seen in numerous roles in Film and Television.  Some of the most notably, Rocky Two, starring Sylvester Stallone, Fast Times at Ridgemont High starring Sean Penn, Scarface, starring Al Pacino, Forever Young, starring Mel Gibson and Where's Parsifal starring Tony Curtis, Orson Wells, Peter Lawford, Donald Pleasence, Ron Moody and various other co starring roles in television.  Ava Lazar is also a producer of three feature-length films, Nature of the Beast with Eric Roberts and Lance Hendrickson, Mic and the Claw and Trafficking.

Francisco Reiguera: Francisco Reiguera (November 9, 1899 – March 15, 1969) was a Spanish actor who is best known for playing the title role in Orson Welles’ unfinished film version of "Don Quixote".  He also appeared in the films "Simon of the Desert" (1965), "Major Dundee" (1965) and "Guns for San Sebastian" (1968).

Supporting paragraphs: Filming The Trial The Trial (1962 film)
Answer: Filming 'The Trial'