3. Terminator 2: Judgment Day (1991)
The "Sad" Ending... When I refer to this movie having a "sad" ending, I know that you're thinking about the bit when the T-800 lowers himself into that fiery pit and raises his thumb up, right? That
is the saddest part of the ending, yeah, and to be honest this movie doesn't really even have an actual "sad" ending, given that the T-1000 fails its mission, John Connor doesn't die, and Sarah Connor gets out of that mental asylum. I guess it's sad, though, in the sense that there's still going to be a Judgement Day, and that John Connor still has a
lot to do...
The Abandoned "Happy" Ending... Whereas that ending is, like, half-sad, half-happy, James Cameron filmed a little epilogue that was refused on the grounds that it didn't open up the story for any eventual sequels. And from a narrative perspective, it also kind of destroyed the "time is a loop" nature of the plot that most of the movie work from. Still,
T2's epilogue would have had Sarah Connor 30 years in the future - in 1997, on Judgment Day - narrating how the end of the world never came to pass. And, uh, John Connor becomes a U.S. Senator for some reason.