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.
I didn’t do the whole game in one sitting but I was glued to my chair for hours when I started Deus Ex: Mankind Divided. Remember looking at them time on my phone and going, “huh, it’s after midnight”. Then again later and finding out it was the beginning of daylight savings time. Went to sleep, woke back up, and played all day again. Fantastic game.
One of my fondest gaming memories, too. I was sucked into the world. Had a rough time back then and it was the perfect escape.