My first game purchased was Control! It's a lot scarier than I thought it would be so I have to play with all the lights on and take frequent breaks T-T
My first GOG Purchase was The Witcher 3. I Played The Witcher Enhanced Edition and The Witcher 2 before, but I didn't have to use GOG until The Witcher 3.
Apparently Warsow was my first, although I don't remember buying that, so in my mind the epic Populous The Beginning was first, which I definitely do remember buying because it's ace as hell 🤙