The good ending to Bioshock.
Reason: Because it was the best possible outcome!
The ending to Marvel Ultimate Alliance and Marvel Ultimate Alliance 2.
Reason: MUA1 - Wolverine: "... You're a punk, Fury." MUA 2: Just a cool ending watching Captain America and Iron Man walk off together understanding how different but similar their views are.
Black Ops II Zombie Origin's ending.
Reason: So... interesting... but, mysterious. Baffled.
And Halo: Reach's and Halo 4's Legendary ending.
Reason: Halo Reach - Watching your Spartan be the last man on Reach gave you sense of his loneliness. And watching him make his final stand was quite epic. Halo 4 - Watching John-117 grieve over the loss of Cortana was just... humanizing for him. The entire series, Cortana was the last thing he had in his life that meant more to him than Earth. And now all of it is gone from him.
Legendary Ending -