Philip French at The Guardian has listed his picks for the top ten movie trilogies.
The Godfather Trilogy (Francis Ford Coppola, 1972-90)
The Gorky Trilogy: The Childhood of Maxim Gorky, My Apprenticeship, My Universities (Mark Donskoy, 1938-40)
The Apu Trilogy: Pather Panchali, Aparajito, The World of Apu (Satyajit Ray, 1955-59)
The Cavalry Trilogy: Fort Apache, She Wore a Yellow Ribbon, Rio Grande (John Ford, 1948-50)
The Three Colours Trilogy: Blue, Red, White (Krzysztof Kieslowski, 1993-94)
The Lord of the Rings (Peter Jackson, 2001-03) "One of the peaks in cinema's history of creating epic fantasy for the screen."
The Bill Douglas Trilogy: My Childhood, My Ain Folk, My Way Home (Bill Douglas, 1972-78)
The Dollar Trilogy: A Fistful of Dollars, For a Few Dollars More, The Good, the Bad and the Ugly (Sergio Leone, 1964-66)
The Scream Trilogy (Wes Craven, 1996-2000)
The Bergman Trilogy: Through a Glass Darkly, Winter Light, The Silence (Ingmar Bergman, 1961-63)
I guessed Godfather, Apu, Three Colours, LOTR and the Spaghetti westerns, and kick myself for forgetting Bergman's "Faith Trilogy." Star Wars, Indie, Terence Davies, The Matrix, Lindsay Anderson, Andrzej Wajda and István Szabó were all near misses.
