Oh boy, top playtimes.
I work a lot in RPG Maker, I play Gmod, Killing Floor, and L4D2 with friends a lot. I like Resident Evil 6 and have played the main campaign all the way through twice, various chapters with misc friends, and done a lot of mercenaries/multiplayer. Terraria is friends wanting to play, as is TF2. I have a second playthrough with friends going through in Borderlands 2. I played PayDay 2 a lot when it first came out.
Resident Evil 5 would be WAYYYY up there if it included by 360 time, I've played over 650 hours on the 360, I never seem to say no to friends to play the game co-op with them. XD; Resident Evil Revelations 1 is mostly playing the main story on Infernal and a lot of Raid Mode. Revelations 2 is just a game I took my time in, played Raid Mode, and did bonus things in.
Evil Within is just a really long game, that time is my blind playthrough of the main game and its DLC, and then an Akumu run that is partial, and taking time to find all the map pieces before their locations were known.
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Evil Within is also tied with three other games at 45 hours:
Killing Floor 2 I play with friends, Deadly Premonition I love and most of that is me doing a 100% playthrough (all side-quests and taking my time and enjoying). Alan Wake is from two playthroughs on PC, both of them taking my time and enjoying it (it's a game I enjoyed, if this included my 360 time it'd be over 150 hours easily).