What brings me back are a number of things:
Films that made a big impression on Dogfood in his childhood, when he was Puppychow.
Lucas, for one, is very interested in the scholarship of Joseph Campbell on Myths and the universality of certain themes on Humankind. One of the reasons the Star Wars sextet (potential nonette?) grabs hold is its population with the archetypes of mythology: the young hero and his life journey, the trickster, the old wise man, warriors, clowns, many more Dogfood cannot recall . Mythic films continue to fascinate- and I don't just mean films about mythology like Jason and the Argonauts, either.
Films that leave one with a positive message. I know life doesn't always work out happily, and maybe this is why the ones I return to fly in the face of the frequent tragedy of life. American films take this conceit to an extreme, however, and essentially do an inverse desensitivation of the public to where they demand happy endings.
Coming-of-age films. An extremely potent subset of the great mythic themes.
Epics. Films you can really get your teeth into. Usually long, and, oddly, can violate the "has to have a happy ending" requirement.
Fantasy/sci-fi/horror. People seem to yearn for something that takes them away from reality.
Mystical. Films that deal with the transcendental or the religious experience, a subset of the Mythic, frequently worked out in fantasy or sci-fi or epic form. Some of Dogfood's faves: The Ruling Class, Last Temptation of Christ, Barabbas, A Matter of Life and Death, 8 1/2, Lawrence of Arabia, Andrei Rublev, Close Encounters, Here Comes Mr. Jordan, Major Barbara, The Passion of Joan of Arc, any of a number of Ingmar Bergman films, and various British "long forms" such as I Claudius and Edge of Darkness.
Great War films. The elemental, ultimate sport of males. Not too appreciated by females.
Film Noir. Films made for the returning GI's from WWII, as solice for men who found that peace completely lacked the transcendent excitement of being involved in the greatest conflict in the history of the planet. Plus, the films have held up extremely well, even/especially the "B's.
Cartoons.
Great World Cinema. Some are so heavy they are essential viewing, but you only want to see them once, or once every decade or so. Still, some are so heavy you have to have them around so whenever you might have that urge...
Anyway, these are the things that click for old Dogfood.