For me it was Terraria, Satisfactory, Tetris Effect Master Mode, Minecraft with Mekanism mod & CSGO / CS2 (almost 2000 hours in CS alone).
Edit: There are so many answers that I might only reply if I have something interesting to say. I will read all of your answers though. 🙂
Edit 2: It has become too much for me and I have to disable notifications. Thank you for the massive response and please continue to discuss with everyone here. ❤️ 🫡
Oh shit, how could I forget gmod. Those were good times.
I still get sucked back in for a week or so every now and then. I never was much for the multi-player, I like taking big city maps and furnishing all the buildings in them and making up little backstories for everything in my head.