The Longest Games to Sink Hundreds of Hours Into

Star Citizen

Though it's possible that Star Citizen will never be complete, what's available now in the game's Alpha version is still extremely extensive. 

While still missing many key features, there's plenty to do between combat and delivery missions, mining and trading, exploration, and direct interactions with other players. If you've ever wanted to go explore the stars in the most ambitious video game universe ever conceived, Star Citizen is the ultimate sci-fi time sink.