To use another example, if they decided to make a JSA movie, which title should they use?Probably. If titles like those had become iconic over several decades, people might not think of them as weird or silly.
Justice Society
Justice Society of America
JSA
All-Star
On that note, how about...?As for title, wouldn't Superman and Batman: World's Finest work if they did want to go that route?
It could, I suppose, but I doubt they'll want to. It's kind of an upbeat title, not in keeping with the grim-and-gritty tone that DC movies seem to feel compelled to strive for.
Superman/Batman: World's Darkest