The first Final Fantasy I played was indeed FF1 and while it holds a certain place in my heart, it just doesn't hold a candle in my opinion to my favorite one, which is FF8.
I think it's generally a split for some people, where a good portion of the folks end up making the first Final Fantasy their favorite because it introduced them into the world of it all. They learned everything while playing the game and it allowed them to become more adapt at playing later or earlier games afterwards.
Then, on the flip side, other people play one Final Fantasy, either enjoy, or don't enjoy it, then decide to try a different one and fall in love with that one instead. Maybe because it's different from the first one they played, or they might just enjoy it more. Or maybe it augments things from the first game they played in a way they enjoy more. It's tough to say, but to each their own I say.
Take care all.