The ending to a game can decide whether the whole expreience of flying helicopters, skydiving, killing hundreds of men, cawling through mud, blowing up buildings, travelling to a deserted island and setting up a cocktail bar is worth it. Sometimes it is, and you walk away from the game feeling a sense of achievement. And sometimes, it isn't.
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An example: Fallout 3 before Broken Steel saved the day. There's nothing more annoying, dissatisfying, and downright stupid than playing through a whole game, only to find that you die at the end.
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Remembering that got me to thinking: what other games are there that end really badly, and can bad endings ruin a game? What better place to ask than here? What do you have to say?