We are talking about One Piece world and not real world so Gensui is superior to other ranks
I think it was stephen who pointed out that the Navy in One Piece has distinctively Japanese elements about it. So it's similar to wherever it is Zoro is from; it's not Japanese so much as it's Japanesque..
Being Fleet Admiral is being the lider of all the fleet, being Admiral is just being a superior patent
Again, Gensui and Taisho are the same rank, but one is a honorific. Fleet Admiral is a convenient way to refer to him, but it's not correct in the strictest sense.
So Sengoku is above Kuzan the Ao Kiji and other Admirals because he was nomeated by the world goverment
Precisely; not because of rank, but because of favoritism.
And no matter what he's still the one that gives the order to all the other Marines and only as to respond to the Gorousei himself
Well, that depends on the World Government.
He absolutely has to answer to the Gorosei, but there's the question of how the World Government is structured. There may well be other civilians who outrank Sengoku, but who are below the Gorosei. They might even have their own equivalent of Donald Rumsfeld wandering around Mariejoa somewhere.
This what I think and I won't change my mind until Oda says differently
See, I'm on the same page. Until Oda says that Gensui does not function in the same way that it does in the real world, I can only assume that he intends to use it in the same fashion that it would be used in the real world.