It was the first one I played. Maybe it makes a difference what one you play first?
I agree. FFVII's probably my favourite, and it was the first RPG I played. It also makes me feel quite nostalgic when I hear it's songs and stuff.
FFX - Almost my favourite, loved the storyline, soundtrack, range of difficulty (dark aeons), and I liked the whole sphere grid system.
FFIX - Completed close to 100%, but the storyline was lacking a little, and it was far too easy.
FFVIII - Very difficult when I was younger, but I thought the ending was great.
FFVII - First one, very good all round.
FFVI - Very good, never got round to finishing it though. (Graphics whore? Probably)
Hmm... I guess FFVII's my favourite, then FFX.