Spear of Destiny
Technically, it would have to be Ultima Underworld though. Anyway, I remember my brother telling me about this totally new game, "Doom", which he played and thought was both creepy and fantastic looking. During that time, I was a member of a club for young kids who enjoyed video games, named "club 8-12"(for kids from age 8 to 12, you could step into "club ado" when you were 13 years old or older). It was based on an old building not too far away from my home. Inside, you had ping pong tables, billiards, but obviously the real stars were the computers and the 20+ TV setups with different consoles plugged on them (SNES, Genesis, PS1 and N64 later on, etc). Every Saturday and Sunday, I would spend my time for the most part of the day at that place. It was like a paradise for me. They had a gigantic library of games for every platform. All the games that were "cool" back then, they had them. All you had to do was to reserve a game and a spot and you had it for an hour at the very least.
Anyway, as soon as my brother spoke to me about Doom, I thought the club probably already had a copy of the game. I ended up reserving a 386, looked at the games they had, but didn't see Doom. I was a bit disappointed so I simply left the computer and decided to play something else. Later on, during that day, I passed by someone playing a really cool game, one that looked like a FPS where you would shoot people with guns, grab meat off the floor and obtain treasures and chalices. I thought I was witnessing someone playing Doom. In the end though, I spoke to the guy who was playing and asked him when did they installed Doom on the computer, telling him that they didn't have the game this morning. At that point, he looked at me and said "That's not Doom, we won't have it until next week. This is Spear of Destiny! We have this game for over a year!"
So yeah, I ended up booking another 386 and play Spear of Destiny for the rest of the day. Can't believe I actually beat Spear of Destiny before Wolfenstein 3D lol