"If I was stranded on a Desert Island, I would want to take....!" (take two)
Destiny - For that endless grind.
Dark Souls Endlessly replayable and the lore speculation would keep me going for an eternity or two.
Mass Effect 2 - It was the most fulfilling game of its type I have ever played and I have completed it 8 times.
Dragon Age: Origins - It always takes me at least 55-60 hours to beat it and that's without reading up on all of the codices. Plus, it helps that I actually enjoy those 55-60 hours.
NBA 2k15 - Having looked at the requirements to get my MyPlayer into the Hall Of Fame I think it'd get rescued before I managed it.
Far Cry 4 - There's simply tons to do and it doesn't get boring. The missions are action-packed and fast-paced. And it's visually beautiful, too.
Zarmena J. Khan
Metal Gear Solid: Peace Walker - Takes about 25hrs to finish the main game but thats really when it gets going with extra ops and the versus mode ive still not completely done everything and my latest playthrough is about a 163hrs so much to upgrade and build for every item and weapon plus completely build up motherbase and the missions are infinitely repayable you can keep going back to improve your rank and find new stuff also co-op means you can just play it forever helping noobz progress through the story or help old hands take down A.I weapons.
Kingdom Hearts 2 - I'll be damned if that sephiroth fight will beat me!
Final Fantasy 14 - As it will always getting updated with content.
Fallout 3 - As I don't think you can ever see all the game has to offer.
Dota 2 - For the near-endless replayability. Mastering a character in that game could take months, and there's well over 100 of them to play with! Add in Valve's constant, regular updates and there's always something new to mess around with.
XCOM - Long War
Skyrim - I haven't played it and would be a good time to start.
Civilization V - Endless hours of fun and im too close to the 700 hour mark now.