I think films, books, or plays all need satisfying conclusions - which is not the same thing at all as having everything resolved. A satisfying conclusion, which is merely the end of the running time or the pages, can be a complete resolution of the issues/mystery or it can be open-ended, either posing further questions of the reader or audience, leaving the ending open to interpretation - the good old did he/didn't he conundrum.
What most people mean by satisfying is usually 'neat resolution' - but it doesn't necessarily mean that. If the consumer leaves the subject feeling more engaged than when he started it, that surely is satisfying? If I'm reading a light novel (on any subject), I probably expect to have all the ends neatly tied up, as I would of a film of similar ilk. If I'm reading something by a more intellectual writer, I might find that the main character is just left in the middle of the subject, with no 'finish' in sight. If he's left with several options of recourse, then it leaves me pondering which he's most likely to take, with what outcome. That can be just as satisfying (because it's allowing me to have an imagination) as the main character winning the girl's heart/making a million/avenging a wrong, etc., and drawing the issue to a close.
If it's a fully factual book or film, I don't expect the facts to be fictionalised - we know that the Titanic doesn't limp back to port, we know that the Hindenburg wasn't retired in 1950, we know that Bluebird's run ended in fatal disaster. So there's always that certainty of ending. What would make for a satisfying ending (and start and middle) would then hinge on performances, dialogue, production values and overall veracity. Wouldn't it?