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. ❤️ 🫡
Morrowind was my big single player addiction. Oblivion and Skyrim were cool but they just never hit quite right.
Multiplayer I was heavy into Halo and Rappelz (some Korean MMO). I woke my brother up by sleep-playing halo, sat in front of the TV wiggling my thumbs on air, and shouted “THEYVE GOT THE FLAG”. And would frequently have dreams where the conversation is being held in a floating chat box from rappelz.
Halo 1-3 are some of the best games ever. I played so much of those games and don’t regret a moment of it.