People keep wondering how WB/DC can set themselves apart from the Avengers, and in my humble opinion, World's Finest is SO the answer. It does so many things in one swipe. By putting the 2 most famous superheroes in the world together, you're instantly matching (or at least approaching) the appeal of a Marvel team-up, and it's not necessarily a rip off of the team-up concept, because it's a pairing, which is different enough. And it's got the contraposition of light and dark going for it thematically, which the Avengers didn't.
It does pose the same complications for a Batman solo franchise that JL did, though. And if it is their version of a MOS sequel, in the sense that it uses characters that MOS2 had to use first (Luthor), then they've lost me. But it beats a copycat effort to make JL any day.