Civilization 2. I was watching my brother-in-law playing it, thinking this must be some sort of simulation that was part of his college homework. After all, I had played F16 Fighting Falcon in my middle school science class as part of an assignment.
But, no, it was a game for fun. I became enamored with it and it began my love for 4X games that continues to this day.
Sid Meier’s Civilization: Beyond Earth. There are other less then stellar games in the Civ franchise that I haven’t played like Starships. Beyond Earth, though, was a day 1 purchase for me, and it wasn’t -terrible-, but it left a lot to be desired.