I.e., games that hooked you in and you couldn’t stop playing until it was finished. Not games that just happened to be unexpectedly short. And by “completed” I guess I mean the main story etc, not 100%ing the game :).
For me, it would be Catherine, Bioshock Infinite and Black Mesa (although I think I got to the final area then had to go to sleep and complete it the next day). I also played an ungodly amount of Hades in one sitting, but didn’t get the “full” ending in one day.
Surprisingly, The Witcher 2!
I believe 3 and its DLC had come out at that point, meanwhile, i had paused the first, which I had bought on release, somewhere before its third act. Somehow I got back into it and finished it in a few weeks.
Then I booted up the second opus and the changes were so drastic! It was amazing! Everything that was a hassle in the first was pretty much gone!
And that story was fantastic, with a proper dilemma at the heart of it : you had to pick a size and stick with the consequences.
I finished the entire thing in a very long weekend, completely enthralled and picked up the third instantly afterwards.
And somehow things got even better!
The Witcher 2 takes around 24 hours to complete the main story. Are you sure that you finished it in one sitting?
There was some sleeping, but at my age, playing a game over the course of one long weekend is definitely “one sitting” ;)