Why is this game reviewing so well 
As someone mentioned relative to a final fantasy game it hasn't reviewed that well. And even for any high profile game of its stature it hasn't reviewed especially well.
Brutal Legend which a lot of people consider a miss has a metacritic of 83. Halo ODST which a lot of people also consider a miss sits at 83 also. Final Fantasy is sitting at 82 right around that company.
Of course those scores are inflated but all videogame review scores are.
The best way to judge a mega franchise is not by the total score but by how it scores relative to how past entries have scored. That's how you know what the general consensus of the review community was relative to a particular entry in a franchise.
Final Fantasy X by comparison has a metacritic of 92. As does Final Fantasy 12.
Of course this is even if someone takes reviews "seriously" rather than just taking them as a collection of opinions and any individual can have his own opinion which is the healthy method of looking at reviews.