Fallout: New Vegas - Longest Possible Ending (29 Slides) 

Fallout: New Vegas is a game where the ending changes based on quests you complete throughout the game. The ending is displayed via slides with a narration describing the effect your actions had on the residents of the Mojave Wasteland. You can miss out on most of these slides though, if you never find or complete the quest they pertain to. This ending might not be the maximum amount of real time, but it has all 29 possible slides included