For me, it's really quite simple.

The first film everything is fresh, everything is old-hat by the 3rd.

The first film generally does not have high expectations (Starwars, Matrix, Pirates fall into this, SpiderMan and Lord of the Rings did have big expectations going in due to their source material).

Based on the Alien franchise and most recently 28 Weeks Later, my rules for big franchieses/trilogies are this:

1) Change Directors with each chapter. You get a different spin on things and keeps things fresh. Fewer Yes-men kowtowing to previously successful director.

2) Follow the world/mythology, not the characters. Explore the themes and ideas of the franchise, not shoe-horning characters back into the saddle after they 'lived happily ever after' following the first film.

3) Do not make everything BIGGER with the sequel. Too much action or CGI ruins the balance most likely achieved with the successful entry. There are times when this works to a degree (Aliens and 28 Weeks Later again...The StarWars prequel trilogy made this mistake big-time)

4) Do not incorporate too many new villains or story threads. Keep the focus of the film tight and focus on the details, not juggling 9 threads. Make 9 damn films if you wish to do that (guilty: most comic book franchises, particularly Batman and Spiderman films)

5) If you plan on making 3 or more films, you are telling multiple chapters in a story or stories, the world/universe does not have to be at stake every single time. Smaller can be better. Nobody seems to understand this.

6) Spend the time and money on screenplay first and foremost. Filming back-to-back sequels is great for saving money, but it rushes the screenplays and doesn't let each chapter develop organically. I'm sure Pirates and Matrix sequels hurt for this.

Oh and I completely dis-agree on the Matrix sequel. The second Matrix film is, for me, the best of the three. I'm not kidding, and constantly get into arguments about this. I just love the new characters, the great computer/programming metaphors, the architect sequence, the staircase fight and chase sequence, and the cliffhangers that were set to pay off big-time in part 3 but the third chapter just didn't bother to follow up the potential and opted for a boring shoot-em-out.

And I purposely left any Lord of the Rings out of this discussion because it seemed to be conceived as a single long film from the get-go. Almost every other trilogy starts out as a successful stand-alone movie (although the writers/directors often claim after the success of the first one that it was indeed conceived as a trilogy...i kinda doubt that in most cases).

I have to agree with you Kurt. The third entry in most trilogies seem to be the weakest. Why? Well I'm not completely sure, but it's been mentioned by Kurt and isn't really that difficult to see for yourself.

I think with, let's say Spider-Man 3, everything just gets caught up with everything else that is going on. I think the studio, producers, directors, writers, whatever just go 'What the heck, let's just throw everything in'. And they do. In order for a trilogy to work, all 3 films need to be different. Think of it like 3 children, all have completely different personalities but sharing a bed with the same cover. The films need to be different, but wrapped in the same/familiar world.

Of course this doesn't have to apply to all trilogies.

Do trilogies really work? Sometimes.

Are they justified as often as they are produced? Not even close.

Did I just create a trilogy of questions that I answered myself? Yes I did.

I'll bet I could sell the film rights...

Thematic Trilogies, where the characters are not carried over from one chapter to the next, often work the best. Here are a few that have no weak chapters:

Park Chan-Wook's Vengeance Trilogy

Krystof Kieslowski's Three Colours

Gus Van Sant's 'meditative/death' trilogy consisting of Gerry, Elephant and Last Days)

Lindsay Anderson's Mick Travis Trilogy (If..., O Lucky Man!, Britannia Hospital) is about three stages of a mans life.

François Truffaut's Antoine Doinel films (admittedly there are 5 of them, not 3!) also do this very well.

Finally Nicholas Widing Refn's PUSHER trilogy has each part deal with three characters involved in different aspects of dealing drugs and all of them are bloody fantastic.

So I guess what I"m saying is that art-film trilogies tend to work more often than Blockbuster styled trilogies...probably due to the fact that art films focus on themes, mood and style where as Blockbuster films typically focus on special effects and story plotting.

Thanks for letting me ramble on this subject Richard.

I think I agree with pretty much all the comments above. In a nutshell (& only repeating some of the above) I think trilogies can work, in fact they can work really well, provided enough effort is put into them.

Effort doesn't always mean money, or special effects, I mean the art films are a good example reflecting this. Above the rest I'd say that the time they put into it at each and every step of the process should reflect in proportion to the scale of their budgets but they never really do.

Story & screenplay probably gets the least and needs the most time, but at a guess this will be studios setting unreasonable deadlines as they simply see it as an asset that will make a return. They're not necessarily bothered if a series dies, they'll have other assets crawling upto them every day.

.. & so I think it burns down to a battle between the creative team & the studios that ruins trilogies'

The "bigger than the previous one" is a definite bad idea. Also I think that most movies that end up being called trilogies suffer from not being designed to be a threesome right from the get go. Usually it's a make money as they go approach... if the first one makes a bunch of cash, go on to number two, if THAT one does, do a third.

Vic

Well what about other successful trilogies like Back to the Future and Indiana Jones? Nobody's got a problem with them?

I must say although I loved The Godfather III it was not as excellent as the first 2.

Well I was hoping that some people would pick up on these. The second Back to the Future is nowhere near as strong as the other two, and that's the same for Indiana Jones.

I thought those might be quite hot discussions, obviously not!

Same with Jurassic Park eh?

Indiana Jones was styled after old adventure serials. By their very nature, films like this almost demand sequels. Granted, Raiders of the Lost Ark was a definitely more closed-ended than its inspirational works were. So were the two films that followed. No cliffhanger endings to be found here. Even still, the effect is the same. It just seems to be a series that leaves one wanting more.

Ditto for Star Wars.

Lord of the Rings really just speaks for itself.

One series I'm not afraid to say was a mistake to expand into a trilogy was The Matrix. And it's The Matrix that I keep finding myself comparing to Pirates. The first chapter was fantastic, then the follow-ups just went too far.