generalfrevious said:
Thinking on a philosophical point, maybe the reason third installments suck is that the universe is binary (one view and its opposite view), and no human being can conceptualize a third view, so we have to rehash or go off the deep end to in the third installment of a franchise.
I think this is part of it. If in part one you consider one angle, and in part 2 you explore its opposite... what's really left?
I would like to also reiterate my philosophy from post #1- The worse #2 is, the better chance #3 has at being good. Generally (but not always) the rule of sequels is they get worse as they go on, but sometimes they hit the bottom and bounce back. See Episodes 2 & 3 of the Prequels (yes, I first didn't mention it because #1 it is part 6 and #2 I like to pretend it doesn't exist).
See also Star Trek 2,3,4. After letting someone other than Nicholas Meyer make 3, they learned their lesson and let him return for #4. (Then they forgot it for #5 and remembered again for #6)
To be self-referential (again), http://originaltrilogy.com/forum/topic.cfm/Act-Breaks/post/433382/#TopicPost433382 this thread. The whole thread (minus the usual fluff) but especially from that post and the next several and most of them through until the end. Looking at trilogies as macro examples of the three act structure. Especially comparing Return of the Jedi to Pirates of the Caribbean 3. While we found easily recognizable three act structure in parts one and two of the trilogies, there was a slight issue with the third parts.
In the terms of RotJ, we found no internal structure to the third part and only found resolution of the macro structure, and resolution of unresolved character issues from parts 1 & 2. A small portion of RotJ (the first third) seems to have its own mini act structure. Then the rest of the playtime is devoted to the bigger story. We wondered whether this was a cause of Return of the Jedi's apparent weakness? Or a source of its strength?
PotC3 was both similar and different. The first part (roughly a third?) was devoted to its own "rescue the hero who was captured at the end of part 2" bit. But then the rest of it, instead of really giving over to resolving the macro problem, seemed to introduce a lot of new elements (the pirate counsel, the sea-witch, whatever else I've purged from my mind).
Comparing this "introducing new content" to RotJ's "resolving old content" is interesting. I find both movies to be disappointing sequels, but I'm generally pretty happy with RotJ as it wraps up the macro storyline (despite its inclusion on the "known duds" list above) and find PotC3 to be all but unwatchable. That being said... Appealing to just these two examples, one can not make a conclusive statement as to whether having its own TAS (PotC3) or simply serving the resolution of the Macro TAS makes for a better finale to a trilogy... But I'm leaning toward this thought:
Not having a rigid three act structure in the third part of the trilogy is a risky business. In the first place, it creates a flexibility and a lack of competing content which allows the movie (or whatever) to resolve the unresolved from the previous parts, and to make good on the unmadegood promises of the previous parts. Cramming all sorts of new content in there iprevents the movie from doing that. However! (This is an important "however") It also means that you need to have enough stuff to properly fill out your two hours (or whatever). It's like walking the tightrope without a net. It's great when it works- it's disasterous when it doesn't. So, when you're making the grand third part to your trilogy, you have to either play it "safe/mediocre" and make a film that can't be fulfilling... or play it dangerous and make a film that can exceed expectations... or completely fall flat. Whether is succedes or fails depends on a lot of factors, including the intrinsic interest in your unresolved story and character threads... and on your competency as artists to work without a net.