The underlieing difference of opinion seems to be in our approach to what is the unit that should embody a complete narative. You say that it must be 1.5 to 3 hour movie that you see in one sitting. I say that it is the complete story that the writer is telling. The vast majority of movies that have been made do complete their story within a single movie. However, that does not mean that that is the only form that is possible. If someone has a story that would take 5 hours to tell (or 9 -> 11 in the case of Lord of the Rings), your rules would dictate that those stories never be told on film (since theaters wouldn't want to show movies that would have that few screenings per day, and studios would have no hope of recouping the extra budget from required single release).
I think that it is a perfectly acceptable option to break such stories up into 2 or 3 pieces. It can be reasonably argued that a particular story does not really require that much time. Maybe the Matrix is a story that didn't need to be stretched out that long. I won't realy know until after I have seen the last one. I *would* contend that LotR has plenty of story and character development to warrant the 10.5 to 11 hours that the 3 extended edition DVD's will total.
You, sassy, have a strong preference for movies where the story is short enough to be told in one movie sitting. That's fine. I have a strong dislike for slasher flicks. Therefore, I just don't go to see them. Why don't you save yourself the aggravation and just not go to see the movies that aren't going to fit into your preferences? Virtually all of the movies that you have named as violating your "ending rule" (to coin a shorthand term for it) there was a *huge* marketing compaign saturating American society before and just after the movie's release. All of those campaigns basically screamed at the public "This is Part 1 of 2" or "This is Part 2 of 3" or whatever. The marketing people did this specifically to avoid having many people be surprised by the lack of closure by the time the credits rolled and being alienated to the point of avoiding the finale (or next installment). Therefore, it should be easy for you to spot these movies before you actually see them, and then not bother to go see them.
This is why I don't agree that they are "ripping off" anyone. They are not pulling a bait-and-switch. They are telling everyone up front that what you will be seeing is the first half, or first third, or middle third, of the story. In order for someone to go into the theater expecting closure they would need to disregard everything about all of the marketing blitz etc. based on the assumption that "It couldn't be what they described. It must fit into my preconceptions instead."
BTW: There were definitely B5 episodes that did not have "endings" at the end of that week's broadcast. A Voice in the Wilderness, Part 1 and War Without End, Part 1 did not have endings. You are just more tolerant of seeing "To Be Continued" at the end of a TV episode than at the end of a movie. Again, that's fine. Your preferences are your preferences and noone is trying to tell you that you can't / shouldn't have them (at least I'm not). However, your preferences do not define the way *everything* *must* be in all cases for everyone.