thanx to the guys at x360a
To 100% the game you will need the following done:
* Complete the story on either Normal or Hard AND New Game +
* Complete all side-missions on BOTH save files
* Complete all 400 Riddler Challenges once (data is shared on both save files)
* Obtain all Gadgets and Upgrades once (data is shared on both save files)
* Obtain Gold on all Riddler's Revenge challenges (as Batman)
In other words: You will have two save files. One on either Normal or Hard difficulty and one for New Game Plus. You will need to complete the story twice, complete all side-missions twice, complete all 400 Riddler Challenges once, collect all Gadgets once, purchase all Upgrades once and complete all Riddler's Revenge challenges once.