For a while there was Oblivion, then Skyrim. There's no such game now
Iliwion and then Skyrim.
For me it's Dark Souls III (I don't know about the other parts I haven't played) really wanted to give up the game hundreds of times after each death and still came back to it and finally passed it.
Warframe 740+ hours. And wow of course. 800+ days, how many hours count yourself)
Warframe 740+ hours.
I remember a time when Fable: The Lost of Chapters really pulled me in. Even if you didn't do the quests, but just wandered around the world, admiring anything and everything and enjoying the gameplay and atmosphere - even then. It wasn't so much the story as it was the gameplay and atmosphere that pulled me in. Once, all at the same time, there was a case where I played it for a full 12 hours: from 12 to 00 hours. And I was just a teenager then, and such things for me personally - were very rare...
And if we talk about the current time - it's probably the recently completed King's Bounty: Legend of the Knight: passed in the same breath, at the weekend I could at least the whole day in it progamat.
The banner saga, X-com, mount and blade
I also pulled in Fallout Shalter for a couple of weeks.