Here's how WB and DC should have done this:
-After the past Batman and Green Lantern movies, have the upcoming Superman movie feature have both characters make an appearance( Although Bruce and Hal would be recast for obvious reasons)
-Finally get the Wonder Woman project off the ground like they should have done years ago and then have Flash, Aquaman and Hawkman make an appearance
-Have the Justice League movie come together with Superman, Batman, Wonder Woman, Flash, Green Lantern, Aquaman and Hawkman teaming up to fight the Legion Of Doom, namely Lex Luthor, Joker, Reverse Flash, Sinestro, Black Manta, Cheetah and Grodd. In the end, Apokolips and New Genesis are mentioned which will build up for the next movie.