This may be controversial, but James Gunn's Superman sequel shouldn't feature Batman. Give Supes some room to breathe before the Dark Knight is introduced.

Zack Snyder’s Man of Steel deserves a lot of credit. The Christopher Reeve Superman movies had become such cultural icons for the character that the one time prior to Man of Steel that anybody tried to make a new Superman movie, they just tried to make a Christopher Reeve movie with different actors.