A trilogy is a pretty abstract notion. You can apply it to almost any three things.
Honestly, I'm not a big movie buff in general. The only movies I own is probably the 'Indiana Jones' trilogy.
One of the traps or the pitfalls of writing a trilogy - or a triptych, or whatever term you want to use - is that the second book can be a long second act to get you from book one to book three, which borrows all of its energy from the first book.
My gut feeling about sequels is that they should be premeditated: You should try to write a trilogy first or at least sketch out a trilogy if you have any faith in your film.
My father loved 'Godard and Truffaut.' He was more artsy. My mom loved the 'Bourne' trilogy; she likes big blockbusters. She loved that I did 'I Am Legend.' My passion for acting came with my passion for movies.