But after the kind of terror The Joker instilled in The Dark Knight, to have some guy come in and start stealing identities and making people solve complex riddles would be a step down. It wouldn't be as entertaining, and he wouldn't truly be a real menace. He would never be able to be the main villain in the movie with motives like that. Now if they were to make him more sinister, then maybe. But If not, Riddler would be another villain very much like Scarecrow, as bad as it pains me to compare the two. Scarecrow can most definitely be menacing and sinister, if Nolan would let him be as such, instead of using him as a throw away villain.