The game can end in several ways. One is a sad but good ending. One is just a good ending. One is a happy and good ending. One is a happy and great ending. And it can also end with Spira blowing up. Just depends on how you play.

Also, when a movie doesn't end the way that you think it should, that's usually an indication that you were not paying attention to what was actually important in the movie. And if you think that, you may be dissappointed by the sad but good ending, when actually that ending is rather telling of what the story makers were trying to portray.