According to Eidosannual reports they "own 25.1% of Rocksteady Studios (London)." And they have done so since 2005 i believe. So Rocksteady are very close to Eidos and they wouldnt be doing a Batman game if Warner Bros didnt buy 20% of Eidos a few years ago. So i think the responsibility for the success can be split into three portions between those three companies;

Rocksteady: 74,9% , Eidos 20,08% ,Warner Bros: 5,02% :roll: