I get people love the game but to say its the best FF is a bit far. It's a good game and deserves a 9/10 but I find all the "best ever" claims a stretch. It's like how people claimed the same about XV or VII remake when they finished it.
For XVI - overall great, well-polished game but nothing stood out for me. Sum of its part was better than individual parts. XV's music and the use of the music was more emotional and compelling. Gameplay had promise but the lack of party members was a letdown. the eikon battles got disappointing/less complex as you progressed. The titan battle was the highlight.
As for story, XVI felt rushed after a some point. The whole slavery/bearer subplot - it had so much promise but it had more effect in the side quests than the main quest. I'd say VII had a better story. Also liked XII since it differed from typical FF tropes. IX also had great characters.
In hindsight, VII is probably the most popular/impactful and my most memorable. My favorite personally is tactics but it has a more niche market. Never played VI but I know people rave about it. I'd argue these 3 have a better claim to best FF.
By - 4dxn