1. Spielbergs Alien Encounters Trilogy
The Films: Close Encounters Of The Third Kind (1977), E.T. The Extra Terrestrial (1982) and War of the Worlds (2005).
Why So Awesome: With a large time gap between the second and third film, not to mention a plethora of other projects, this doesn't initially seem like the conventional grouping. But when you think about it this is in fact the perfect unofficial trilogy as it actually tells an overarching tale. The stories may not be linked (no matter what some fans theorise), but their messages can be. First we get initial encounter - aliens arriving at Earth and that mutual curiosity developing into obsession - then the humans first move - that development of emotion with the people juxtaposed with animosity from the powers that be - and finally the aliens' violent move - their much superior technology trumps ours, but in the end its biology that wins out. It presents a realistic development of how wed develop from first contact and adds extra subtext to two great and one OK film.
Have you got any more unofficial trilogies? Let us know in the comments below.