Wow. From my observation, 95% of these 'best FF ever' or 'Worst FF ever' end up erupting into flame wars, over unnecessary defensive-ness or just being unwilling to expect other people' opinions. How sad.
No FF is bad in my opinion. Although If I had to pick the worst I'd probably be FF9, even though it is a really fun game. I thought the gameplay was too simple, and the only mindbenders in the game (besides Necron) were the side quests.
All FFs have been great, but I founf FF9 to be the least spectacular.