Honestly I don't think the game needs to have a ridiculous game length. That's one of the things I loved about Spiderman and God of War. I was able to sit through the whole game and enjoy it. I have always had difficulty finishing a game, either because of life or another game popping up. So 40+ expectations just for story would have been difficult for me. While I would have loved to play for longer and enjoyed more of that world. More time does not mean better.
Just look at Persona 5 (I love that game don't get me wrong) a lot of that game is grind and waiting. Now they made that a lot of fun, but because I didn't spend any extra time grinding in that game the ending became more difficult to get to. Artificially inflating a game time by requiring grinding is not my idea of a good time.
Basing the hours of the brothers seems a little iffy. Yeah they did some side quests but I feel a need to stress the some. There is still plenty to do. 28% can be a lot. Especially if what's left is mini games, bosses, synthesis, keyblades, etc. Most of those may only count if you actually complete them. That could be a surprising amount of play.
As for the ranking? Many of those have been placed on glorious pearly pedestals. We've had time to love those games in spite of some of their flaws. To know every little detail about them. To understand every secret, every question, every answer. Even Chain of Memories, a game I have unfortunately never finished due to my distaste for the card system, has a special place in people's hearts for it's stories and characters. Take a look at anyone's ranking for this series and you will see a large variety. Especially since some games aren't even on that list.