I've been thinking recently that prior to the Crisis, DC was known for it's infinite Multiverse and how many heroes would travel to different Universes to team-up with the heroes of that Earth (i.e. JLA teams up with JSA, etc.). I acknowledge that Marvel also has a Multiverse, but DC was the superhero comic publisher to really popularize the idea of an infinite number of parallel earths (with Michael Moorcock creating the name Multiverse & being one of the first authors to have a series based in an infinite number of universes). Not only that but also DC's history is/was really engraved with the idea of multiple earths & there being Earths with their own set of heroes (the JSA on Earth 2, Captain Marvel on Earth S, etc.). That is something that Marvel can't claim since most of the stories (historically) are set on the same Earth nor does Marvel have legendary Golden Age heroes like the JSA.
I wasn't impressed by WB's casting (& creation) of a Flash film since the tv show is performing really well & is fairly popular, however thinking about DC's Multiverse & WB claiming that there will be no cross-over between the films & tv shows has compelled me to think that a good way for WB to counter-act Marvel's popularity would be to say that all the films, tv shows, games, comics, etc. all exist in the DC Multiverse but within their own Earth. If WB/DC were to make a JSA movie, they could say that the characters exist in the DC Multiverse that's occupied by the characters in the BVS film & in the other upcoming DC films. Even the new Shazam film could exist in it's own Earth within the Multiverse.
I believe if WB were smart, this is a route they could take. They could potentially become popular & gain some respect in regards to their characters & Multiverse. I believe if they were to take this direction, they would prove to be more ambitious & I believe from a fan standpoint, it would be really interesting.