Phantom of the Paradise is one of my favorite movies. The ending seemed like a cop-out when I first saw it, but on rewatching it (several times over the decades) it’s grown on me as being the only way things COULD have ended.
The happy ending. Hope for humanity, a recovery may be possible.
Neville dies (in a crucifixion pose, no less. Beat us over the head, willya?)after synthesizing a serum and makes sure the other surviving. but non-immune humans get it. it;s also weakly implied that Mathias’ family and the other mutant survivors are dying off, but more from impending starvation rather than the plague.The ragtag band of survivors take the serum and move out of LA.
Not the ending of the book. I love both version though.
And Chuck is Chuck. Moses parting the red plague. It is what it is. 
Similarly, the 1994 HBO adaptation of Robert Harris’ Fatherland ends with a revolution that brings about the collapse of the Nazi regime, as opposed to the ambiguous ending of the book.
As I recall the novel based on the movie did it somewhat better.
It still had the modern military force vanish before doing much, but it turned out that the two people stranded in the past had been working with the government in the intervening decades to develop advanced technology based on their information from the future. It had just been kept totally secret all that time to preserve the timeline. But now that the time-loop is completed, the cover can come off all the goodies they’ve developed. A bit tacked on, but more interesting than “oh, and then nothing happened”.
I’ve not seen it, but the ending to Final Countdown sounds like it’d be really hard to write satisfyingly. F-16s versus IJ Zeroes? How do you make that fight remotely interesting? It’d be like Mike Tyson fighting Stephen Hawking. You have to find something more interesting than just 10-15 minutes of American jets obliterating WWII era propeller planes, although from what people are saying, it doesn’t sound like they quite found it.
“Yeah, just try me…”
lol “Larry Flynt is right!”
From what I understand, they ran out of money and the planned big battle at the end had to be cut. They made do with the 4th wall ending because it was cheaper.
Nitpick: The F-16 is a relatively small single-seater USAF plane; the USS Nimitz in 1980 carried the much larger and more capable F-14 Tomcat.
Anyway, the only action between the U.S. Navy and the Imperial Japanese Navy in the whole film was one brief skirmish between two F-14s and two Japanese Zeros. And you’re right, it wasn’t all that interesting in its own right; it was interesting only because the audience is led to believe this is the prelude to a much larger battle…which then simply never happened.
I wanted to see a high-tech turkey shoot with F-14s striking and sinking all of the Japanese aircraft carriers with AIM-54 Phoenix missiles in anti-ship mode along with precision guided bombs.
Of course, I’m sure this exceeded the special effects available for 1980…but it was still disappointing to get nothing.
Omega was based on Mathison’s novel, but it’s so different the changes don’t really bother me. I like it better than Smith’s adaptation.
In case anyone is not aware at this point, the original ending was much closer to the book but test screenings disliked it so the studio chickened out and reshot the ending. The alternate ending was later put out as a DVD extra and was so preferred it’s now the continuity for the upcoming sequel (also, the alternate ending was the only one where Will Smith was alive which is handy for a sequel). The theatrical ending is now considered non-canon in the IaL cinematic universe.
https://screenrant.com/i-am-legend-movie-alternate-ending-changes-explained/
I’ve read one critic who theorized that the “cheap” look of the film was a deliberate choice – that Python made the movie to look like a bunch of second-rate hacks were making a movie but didn’t really have the know-how or the budget to pull it off. The “horses” gag, with the coconuts, for example. The “end the film because we ran out of money” is the deliberate gag, not that Monty Python actually ran out of money. YMMV.
An additional aside on Omega Man (a person if flawed favorite) -
It did explicitly make the point that Heston was indeed a character of a dead world, clinging to everything from before and at some level, absolutely refusing to let it go. And it was finding the other “survivors” that gave him the impetus to actually make a positive change for the future. Otherwise, well, he was bound and determined to keep fighting the Family until he or they were all dead.
So in that sense, it was quite true to the sentiment of the original work, but as stated upthread, it’s setting/circumstances are different enough from the original to not create quite so much dissonance.
You’re thinking of the opening credits. There are no closing credits.
But there was closing music.
I’m not going to say it’s 100% a cop out, but the ending of AI: Artificial Intelligence sure feels like one.
The hyperevolved AIs (some say aliens) bringing the protagonist back to experience one more day with it’s mother felt like a terrible effort to give a bitter-sweet ending to the story. And it shows (to me, others can feel otherwise) the drastic flaws in the “intelligence” in question - it couldn’t really evolve past it’s emotional fixation on love. It takes the Peter Pan principle and turns it up to 11. It should have played more as a tragedy and end on the sinking below the ocean and sell the tragic elements. Instead we get a “heartwarming” final moment that’s fundamentally a lie.
Of course, I could be overly harsh on it, I watched it once (on an actual Netflix DISC) and was so disappointed I never watched it again.
I think the ending of A.I. is beautiful. I admit I may be the only one. Well ,me and Spielberg.
Could a different ending be better? Sure. Does it fit the OP? It could!
2001: A Space Odyssey. There. I said it.
I haven’t seen the movie made from Michael Crichton’s sci-fi novel “Sphere”, and after reading the book, I don’t want to.
EVERYONE I’ve ever known who read it was, like, “What was with that ending?” I’m not the only one who said that maybe he had a deadline to meet, and that’s what he submitted.
Other People’s Money.
Rather than let the movie end with the gritty lesson of corporate take overs and Jorgys stubbornness helping him lose his company the film makers had to put a smiley face at the end with the Japanese automaker saving the company with airbag production. Weak.