Answer: Godzilla

When it comes to long running film franchises, there is one thing that sets the winner apart from everyone else: continuity. While there have been, for example, more than a few Superman and James Bond films over the years, those films are not contiguous and the franchise is rebooted with each film or after short runs like trilogies.

The Godzilla franchise, on the other hand, is not only over half a century old, but nearly all of the movies are all produced by the same studio. The Godzilla that appears in the eponymous 1954 film is the same as the monster that appears in the 1966 film Godzilla vs. the Sea Monster (a.k.a. Ebirah, Horror of the Deep), and so on right on down the line of movies to the present. As of 2021, there are 32 films in the franchise as produced by the Toho studio in Japan and another 4 films in the American stable of adaptations.