Destiny - Piss and moan all you like, but with friends there is no better shared world shooter. I am up to able a week of gamplay time across all my characters
Final Fantasy Tactics Advance - put more time into this than I really should have. If anyone cares, I have screenshots of my completed file and characters. I beat all 318 missions, but didnt clear all the classes. I would add A2 into this, but I fopped my save and will have to start over again.
SM64 - I do a run of this game once every few years, collecting every star as fast as possible, without cheating lol
Dragon Warrior Monsters - Such a perfect monster collecting game. I have more hours in this game than I can count. So many playthroughs and so many grinding sessions.
Soul Silver - this game stole me away for far longer than I expected. Not that I ddint expect it to be a good game, but I really couldn't believe that I wandered all through Jhoto and when I looked back, I was near 80 hours of gametime.
FF Dissidia - Simple rpg like fighter that can really be played forever. Its so easy to get lost in the FF world of heroes and villains.
Puzzle Quest (mobile) - its really too bad I dont have a way to play this anymore, but the mobile version of this game kept me entertained for hours in college when I was required to go to chapel 3 times a week. I had it first on my old moto flip phone, and then on my enV2, but the newer phone pissed me off because I couldnt answer texts in the middle of the game.