FF3/VI is my favourite game and the first RPG I remember playing. I was ten at the time, and was so used to playing platform games and the like, first time I played it I didn't fully understand what was going on. A few months later I gave it another chance... and I was hooked. I used to rent SNES games pretty much every weekend, and eight times out of ten, I rented FF3. To this day, I never get tired of playing it. It was just so different from every other game I had played up to that point. The first game I played that had any real depth to the characters, with a story that I could get truly involved with. FFVI completely changed my perspective on video games.
I own most of the Final Fantasy games on PS1 and FFX, the big exception being FF Chronicles, and I enjoy them all. FFII from Origins I can take or leave, however. I don't care for the experience system. But for having that and the original Final Fantasy remake on one disc is money I'm glad to have spent.