I remember Brushing through FF6 when I was a little kid and paying attention whenever I saw chocobos, So FF6 as a result never became my favorite, for a while I was sucked into the FF7 crazy fanboy crap because it was the first FF I actually understood. I couldn't stand 8 when it came out but Recently I replayed and have renamed it my alltime favorite, 9 I Loved when it came out but realized the characters looked strange to me, even though in my opinion FF9 had the best battle system, FF10 and 10-2 were passovers for me, I Beat them within a week of getting each.
I started playing FFs when I was like 4 years old, I remember playing mystic Quest and not reading any of the text but fighting everything I could find, the same goes for FF6 which I don't think I Got past the railcar ride during the escape from the Empire thingy. FF7 was my first FF to fully immerse me in RPG so being 7 like 8 years old or younger it took me close to a year to beat it (Keep in mind this is around the time when Ocarina of time was stumping me as well)(I Hated having the mind of a 4 year old at 8 years of age) I gradually got better at playing FFs, I remember seeing FF9 in the video store one day, never even hearing about it coming out, and I spent half a year getting through it. FF10 was completly a passover for me because by the time I got it in 7th grade I learned how to observe my surroundings, I've gone back and replayed FF6-8 beacause I realized I couldn't remember the storylines cause I didn't read them. Couldn't stand 9 when I tried to replay it XD.
Edit: Oh and on the subject of pre FF6 titles, all i have played was mystic quest and FF2 I have never touched the other ones.