The game that fully got me into this PC madness was the glorious Battlefield 3 in 2011-2012.
Before that I had dabbled somewhat into PC gaming, even changing a graphics card and what not, but I was still rather clueless about it... Until EA and Dice dropped this fucking megaton into the unsuspecting world:
https://www.youtube.com/watch?v=-FktL2pu2wE

Nowadays, that gameplay above? It merely looks decent. But back in the dying days of the PS360 generation? That shit looked BANANAS, let me tell you. It was, legitimately, like a generation and a half of visual improvement. We couldn't believe it, it was fucking insane. And that, combined with the start of the golden era of PC and the disastrous aging of PS360, meant that I HAD to get a PC, like a decently built from scratch, purpose-built-for-gaming PC. So I started getting informed and saving for the components all throughout 2011 so that I could be there for BF3 day one on the ground floor.

I ended up saving around 450 euros, and this was back in the day when 500 bucks got you an pretty good computer. I got a Radeon HD 6850 and a Phenom 955, and the latter is still working to this day back in my family's house. Every buck and minute of research was worth it, and it even led me down the road of getting into IT as a profession. I have so much to thank to whoever were the people that made that reveal look so sick lol.