My very first PC game and the reason why my switch from Amiga to PC was made easy: Civilization (1991)
I had an Amiga for 5 years but often played PC games at my friend's house. Most of them felt inferior to Amiga games (prior to 1990) but then things started to change: Wing Commander, Dune 2, Civilization, and more were released. And yes, they were also all still available for the Amiga too, but I never had a hard drive for it and also not a second disk drive. The constant disk juggling was a real chore - and seeing that games became bigger and bigger (meaning more and more disks), the switch became inevitable.
Once I had a PC, the first game I bought (yes, I actually bought it fair and square) was Civilization. I still have it today, the good old MicroProse massive box and manual, in all its beauty, 35 years later.
Do you remember your first PC game?