Films: A Fistful of Dollars (1964), For A Few Dollars More (1965), The Good, the Bad and the Ugly (1966)
Flash memories of film franchises usually contain superheroes and spies, monsters and Muppets, but the most consistent series of all time had none of these things. Director Sergio Leone didn't even conceive of his epic Spaghetti Westerns as a trilogy.
The "Man with No Name" films weren't considered a trilogy until United Artists decided to distribute them that way. But when programmed together, a thematic unity emerges that's deeply satisfying and just plain feels right.
Shot on shoe-string budgets overseas, Leone's work changed the western and cinema as we know it. It's easy to see why Quentin Tarantino (who would have made this list if Kill Bill Vol. 3 had been made) calls The Good, The Bad, and The Ugly his favorite film.
Possible reasons are readily apparent in every rich scene of the trilogy: the landscape is vital to the themes; the performances are prototypically gruff and crusty; the scores astonish; and no other action series has better final standoffs. In particular, the standoff in TGTBTU is a masterclass in that particular set piece.