With the new rumor that Warner Bros is already thinking about the third Green Lantern movie before the first has even finished shooting, I started to wonder: Why are movies so obsessed with trilogies?

It's easy to point to Lord of The Rings as the cycle that set fantasy literature in the direction of trilogy adoration, of course; Tolkein's books had a wide-reaching influence throughout genre culture, and those who seek epic sweep tend to have it somewhere in the back of their mind - but yet, there's something about LoTR that doesn't fit the profile of blockbuster trilogies as we've come to know them... the fact that it's a continuous story that doesn't have an easy out earlier on, perhaps.

See, modern movie trilogies have a very particular structure: The first movie is, essentially, complete in and of itself, just in case it tanks at the box office and doesn't warrant a sequel. Sure, there are threads left hanging to make people want a follow-up, and the core struggle won't be entirely dealt with in order to make the rest of the trilogy possible, but there'll be enough closure just in case it does a Prince of Persia and flops at the box office. Then, the second movie will have a completely arbitrary, unsatisfying ending, and exist purely as complication to the overall series and set-up for the final movie, in which everything will be brought together in, more often than not, a manner that feels oddly artificial and somewhat rushed and ill-considered. Seriously, think about things like Back To The Future, The Matrix or the Pirates of The Caribbean series; they follow that throughline entirely (Consider, also, the trilogy within the Star Trek series, Wrath of Khan/Search For Spock/The Voyage Home: Same thing). And where did that formula come from?

Star Wars.

It's a weird thing to realize that every major sci-fi or fantasy movie trilogy that isn't Lord of The Rings has modeled itself on Star Wars and its following two sequels, right down to their failures (As Joss Whedon put it at Comic-Con,Empire Strikes Back doesn't even have an ending); it simultaneously makes Star Wars seem more impressive, and other movie series much less so. It also makes me wonder what movies would have done without George Lucas, and whether the success of longer series, like Harry Potter and Twilight might make filmmakers realize that there's another model out there to follow that won't scare people off. Even better, it might make them realize that they can do their own thing and still win friends and influence people.

You know it's an odd world when Michael Bay seems trailblazing purely because Transformers wasn't structured as a trilogy from the outset, isn't it?