You're right as far as movie titles go, but the movies are a small part of a larger multimedia franchise. When I'm discussing that franchise in the context of, say, the Trek Literature board, which may entail conversations about books and comics that draw on elements from multiple different shows and movies, then just saying "Star Trek" may not be an adequate way of expressing what aspect of Star Trek you're talking about. Even if it's not the name for any other single work in the franchise, it's still the name for the entire franchise as a collective, and there are a lot of conversations that can involve references to both the franchise as a whole and a specific work within it. So it helps to avoid confusion if each specific work has a distinct title. And I don't think putting the date in parentheses after the title works very well because then you have to type out the whole thing. If I want to talk about Star Trek: Generations, I just have to write Generations and people know what I mean in the context of a Star Trek discussion. That's the value of individual titles -- it's redundant to have to write out the series title when everyone knows what series you're talking about.
It's funny how people noted the no colon business with INTO DARKNESS, because didn't that first happen with GENERATIONS and then NEMESIS, but everyone including Paramount just forgot there's not supposed to be a colon in those titles?
The reason why extra-titular disambiguation is required is irrelevant; when disambiguation is required, it's still required. The point is that providing disambiguation is hardly an insurmountable problem. Besides, as Maurice said, strictly speaking, no disambiguation with any other film is even needed, when talking about the film called Star Trek. There might be some sort of case that Star Trek (2009) could be confused with The Cage, since the only on-screen title to the first pilot was Star Trek, but since we already have a title for The Cage, namely The Cage, that's probably not an actual problem. The situation with First Contact (TNG episode versus film with TNG crew whose subtitle is that) is pretty well known. It might also be pretty easy to confuse TNG: The Emissary and DS9: Emissary. Some two-parters, such as The Best of Both Worlds, lack a formal "Part I" indication in the titles of their first parts. It's sometimes reasonable to add that, say appended parenthetically, to disambiguate the first part from the whole two-parter. I suspect that's sometimes done to conceal the fact that a cliffhanger is about to occur. That's a marketing angle that never really goes away, even though audiences who've already seen it know it's coming. --- Lucas subtitled the original Star Wars film to integrate it into the saga, once it was clear that more than one film would occur. That's not a need that any Star Trek film has had to date.
I've called the 2009 movie "Star Trek" around the board and have yet to have someone ask what the hell I'm on about. I wonder more what this film trilogy will be called (no doubt, "The Star Trek Trilogy" to much gnashing of teeth)
I wonder if the next film will get the subtitle(?) of "Out of Darkness" or "Into Light" or something? At least to get the titling to have a flow, in the "Star Trek Trilogy."
I kinda hope it goes further than three films. I don't want to see Kirk and Co finally on their five year mission turn out to be their last film. Trilogies are overrated.
After the third one, it's gonna be a new reboot with Andrew Garfield as Kirk, Emma Stone as Janice Rand and Sally Field as Klingon.
I gotta say, while it does bug me that Gorkon misquoted Shakespeare in comparing "the undiscovered country" with the future rather than it being 'death' as the Bard envisaged it, I actually kinda like the allusion. I've always justified it as being a comment on the Klingon/Federation treaty meaning that everything 'this' generation of space travellers has known for their entire careers, on both the Klingon and Federation sides, is now effectively dead. "The future", Chancellor Gorkon seems to be saying "is no place for dinosaurs like us". Of course, if Meyer had got his way and been able to use the title for Star Trek II, then the literally quote would have been far more literal.