For the most part, video games haven't been all that big on ambiguous endings. Usually, the main character beats the bad guy and saves the day, and you can leave content in knowing everything is going to be alright. However, a closer look at these apparent cut-and-dry finales often makes them far more interesting than they seem, as there's usually some narrative implications which muddy the waters.
In fact, in some of the most popular single-player games, you might not realise the villain actually won. Yeah, the hero might have killed them or thwarted an evil plan, but there's often larger machinations at work which imply that thematically the protagonist lost, or their actions didn't effect all that much in the grand scheme of things.
It might not be immediately obvious, but these apparent "happy" endings have pretty horrific implications for the wide-reaching narrative which doesn't simply end when the game does, and will completely change the way you look at some of the medium's most iconic stories.