"Lord of the Rings" is the perfect example. The original trilogy, complete with its DVD-released additional footage in the director's cut, probably could have been longer, especially the third movie, "Return of the King." (To be clear, I don't think the movie should have been extended, but it could have been made into two films.)
Then I saw "The Hobbit: An Unexpected Journey," and learned that it it is the first in a trilogy. While I loved the movie and enjoyed "The Hobbit" in book form, the book itself is only 320 pages, and we all know how J.R.R. Tolkien is about describing things. Anyway, I think it could have been accomplished in one film.
As I notice the sixth "Fast & Furious" movie coming out, I yearn for something new - but franchises are less risky, once they get rolling - and they bring in the money.
Are you a fan of franchise movies and sequels? Leave your opinion in the comment area below!