4. Joseph Gordon Levitt
Another excellent match that will likely never happen, Joseph Gordon Levitt has already played a different character in the Dark Knight trilogy which is unfortunate. Casting Joseph Gordon Levitt would either mean that the character of Batman would no longer be Bruce Wayne or that The Justice League would ignore the Dark Knight Trilogy completely, neither of which are particularly attractive options. However, few actors would be better-suited for the role. Joseph Gordon Levitt is a very versatile actor who has become increasingly comfortable in big budget action films, as evidenced by Inception, The Dark Knight Rises, and Looper, but he has also pursued more edgy independent fare. Like Hiddleston, Levitt would be particularly well suited to the playboy persona of Bruce Wayne but, considering that role probably won't take up too much of the Justice league movie, he would have to be no slouch at the other required elements of the character.