One I always loved was the ending of The Graduate. Great example of “show don’t tell” while also leaving you to have to come to your own conclusions about what happens after the screen goes to black and credits roll. The two of them hop onto the bus and are so happy with what they’ve managed to do. Then they sit there and the uncertaintly about what lies ahead sets in, you can see it dawn on both their faces. I like when a movie gives you just enough to go off of and then you can speculate about it after it’s over.
I don’t need to have a movie end with a neat little bow; in fact, I like it tied with a Gordian knot, but give me enough to sort it out.
Antonini’s Blow Up just leaves you hanging without enough information to resolve the issues.
Pulp Fiction is confusing, but all the data needed is there.
I have a horrible habit of comparing movies to the books they created from. I was especially irritated with the ending of Circle of Friends. (Maeve Binchy) The end of the book was excellent, the end of the movie made me mad.
I agree with @filmfann in that I don’t need a tidy, happy ending for all, but I like a recognizable ending — even if I have to extrapolate some of it myself. I can fill in the blanks, just gimme the pieces.
I also like an ending to point to more story to come, even if we don’t get to see it. Not a cliffhanger per se, just that an end is also a beginning or a continuation, like in real life.