The beauty of Final Fantasy is that, with each entry being different from the others, every game of the series ends up resonating differently with different people.
The “best” Final Fantasy varies greatly depending on who you ask, for a combination of factors, including nostalgia and subjective opinions on the different aspects of the game (story, characters, gameplay).
It’s what I love about this series. You may play ten games, but the eleventh will still surprise you in some way. Even if I don’t like a specific entry, I can still appreciate that they tried something new and unique, and I always look forward to playing the next one.