Final Fantasy VII.
I actually had no interest in the PlayStation after it was first announced. I was all about Nintendo at the time. But when it turned out that the next installment of Final Fantasy was going to be a PS1 exclusive, well, I had to buy one. And while I did buy a few other games for my PS1, I spent most of my time that generation playing on the N64.
Yeah, not to go off topic here, but it was really depressing when the PS1 did so well. SNES had all 3rd party games AND Nintendo games. Then along came the PS1 taking all these incredible franchises that had been exclusively Nintendo for the entirety of their existence.
In hindsight it makes perfect sense, but at the time it was just bewildering and frustrating. If you were a hardcore SNES gamer you were pretty much forced to buy two systems now instead of one, just to play all the franchises you liked from SNES.