Final Fantasy VII. I was a huge fan of the series and after renting a PS1 and the game for a weekend, I HAD TO have that game for myself.

I originally had a N64, but i religiously bought a Gamepro every month...i dont remember which game i saw that blew my mind, and i told my mother that had to take me to the store to buy a Ps1.

I rememeber perfectly how the guy that was attending us asked me why i needed i Ps1 when i had the more powerful 64 bit N64 LOL what a shitty salesman.

Long story short, im a Playstation supporter since then.

I remember talking to a friend when the ad came on television.  My jaw dropped and my decision was made.  

I think it was a combination of games that I saw at some friends house and trying mutiple demo disc. When I got a ps1, I spent a lot of hours only playing some demo.

i think it was Dino Crisis, but its hard to remember since it was such a long time ago.

Toshiden if i write this right.

Final Fantasy VII. Didn't care about the PS1 before then, If FFVII had come out on N64 I'd have probably been a N64-exclusive gamer. That said, the PS1 was an RPG lover's heaven and I'm glad I got one.

Gran Turismo. I played it on my cousin's house and loved it.
Also Spyro The Dragon, which I saw on a TV show called "Nivel X" in Argentina, and really wanted to try it.

Final Fantasy 7. Would've bought N64 for it too.

Metal gear solid. And maybe a little bit of GranTurismo