The Witcher 3 comes on top with 127 highest-quality hours for the base game and my first-ever completionist drive. Missing the DLC for now, still haven't had the time to get to it. But I suppose I'll get to 170 hours with that.
Second comes... Destiny, with 95 hours.
Unless you count single-player campaigns on an entire series. In that case, I've played more Halo (Combat Evolved, Halo 2, Halo 3, ODST, Wars, Reach, 4, 5: Guardians, and Wars 2) than even The Witcher 3.
If 343 delivers an openish-world not unlike Destiny, I'd break all my records, though.