We say finally because based on the story of the game, it sounded like it would have been a pretty good movie or series, at least on paper. In case you’ve never played the game before, it is set in an alternate DC Universe where the Joker tricks Superman into killing his wife, Lois Lane.
In the process, Superman is driven mad by his actions and actually kills the Joker and set off to create a world, ruled by him and some of his allies, in which such a tragedy would never happen again. This forces Batman to try and find other superheroes to try and stop Superman from ruling the world with an iron fist.
In fact, if you’re curious about the story, there are actually a bunch of videos on YouTube that supercut all the in-game cutscenes together to form a pseudo movie, so you can watch that if you’re interested. There’s currently no word on when the movie will be released, but its trailer will be one of the bonus features of Batman: The Long Halloween, Part Two’s Blu-ray set.