I'm not sure the first actual game I played, but I know the first game I ever owned was Day of Defeat: Source. I had a shitty laptop and knew nothing about system requirements and assumed any game would work the same as it does on console(ended up probably sitting on just above 30fps if I remember). I also didn't even own a mouse so I played with a trackpad for probably 6 months. I was also limited on how much I could play so I basically played about 3 hours a week but it was the most fun I ever had.