Critical misfire Green Lantern seems to have been an attempt to build a larger DC universe in the world of film, given its inclusion of popular supporting character Amanda Waller and early plans to include a cameo from Superman. But Waller is inexplicably portrayed as an ineffectual scientist rather than the terrifyingly lethal covert problem-solver of the comics, and Superman, of course, never shows up in the film. Still, much as Marvel used Ang Lee's Hulk as loose background for the later The Incredible Hulk, DC could use Green Lantern's cosmic milieu - Oa, the Guardians of the Universe and the Green Lantern Corps itself - to support the notion that Earth lies in a universe of awe-inspiring wonders and super-science.
It would be trivially simple to incorporate this background into a new Superman film. A member of the Green Lantern Corps could arrive at Krypton moments too late to prevent the planet's catastrophic explosion - but not too late to scan the lone survivor's rocket and ensure that the infant Kal-El reaches Earth safely. Krypton's advanced civilization dovetails nicely with that of the Guardians and their Corps, establishing the shared universe as one teeming with alien life, of which Kal-El - Superman - is simply one example.
The Superman film presents a great opportunity to establish a number of important aspects of the DC universe: S.T.A.R. Labs (who could perhaps be responsible for accidentally unleashing Metallo or the Parasite to serve as Superman's antagonist), technologically-advanced and alien-backed criminal organization Intergang, and world-leading newspaper the Daily Planet. Reporters Jimmy Olsen and Lois Lane could serve as supporting characters in this and future films, writing stories not only about Superman but the heroes that appear in his wake in succeeding films. And most importantly, Lex Luthor - who will not appear in this film as a villain, but as a boyhood friend of Clark Kent - will begin his journey as the Justice League's ultimate antagonist, building countermeasures to protect humanity from what he sees as the rising threat of super-heroes.
A rebooted Batman film would appear next in the series, one less grounded in reality than the Nolan films and slightly less dark. This Batman would live up to the title of World's Greatest Detective, battling crime not only with his gadgets and martial arts prowess, but his wits and powerful deductive reasoning skills. In his guise as billionaire playboy Bruce Wayne, he might even cautiously cooperate with Lex Luthor in developing precautionary safeguards against powerful creatures such as Superman, planting the seeds of betrayal and redemption in later films.
To introduce the DC universe's mythical elements, a Wonder Woman movie is the natural next step. During World War II, an American fighter pilot crash-lands on the mysterious Paradise Island, disturbing the peace of an advanced society of matriarchal immortals descended from Olympian gods, gods of super-science rather than magic, much in the spirit of the Asgardians in the Thor movie. Realizing that the war could impact even their isolated island, the Amazons send Princess Diana - Wonder Woman - off to fight Nazis, who in their mad quest for power are pursuing not the Spear of Destiny or the Ark of the Covenant, but the advanced weaponry of the sunken city of Atlantis - future home of Aquaman. Wonder Woman defends Atlantis, sends the Nazis packing, and returns to Paradise Island for the next few decades, "until man's world needs me again."
A second Batman film would widen the scope of the Dark Knight's supporting cast, introducing rival playboy and Batman fan Oliver Queen (the future Green Arrow) and Queen's more grounded on-again-off-again girlfriend, Dinah Lance (the future Black Canary). As an increasing number of madmen and super-villains make Gotham City their home, Batman realizes that he needs allies in his war on crime. He isn't thinking of any kind of official league yet, but after being nearly overwhelmed by a horde of criminals, he'll realize he can't do it all alone. At film's end he even reluctantly accepts Superman's help to repel a brief attempt by Intergang to expand into Gotham.
Ryan Reynolds returns in a quasi-rebooted new Green Lantern film. Already an established hero, Green Lantern faces a series of escalating threats. At first it seems as though the mutants and robots he fights are wreaking random havoc, but he eventually realizes that he's being tested by an unknown agency. Of course, we the audience learn that Lex Luthor and Bruce Wayne are behind the tests.
The next film introduces the Flash, a police scientist who, because of a freak accident, gains the ability to run at fantastic speeds. Aided by his friend and confidante Ralph Dibny (the future Elongated Man), Flash battles Professor Zoom, the Reverse-Flash from the far future who time travels in an effort to prevent the formation of the Justice League. (Of course Flash doesn't know this, but the audience does.)
In Green Arrow, Oliver Queen and Dinah Lance face separate perils. Their yacht boarded by the League of Assassins, Queen is marooned as useless on a desert island while Lance is kidnapped and forcibly inducted into the League, for according to their prophecies she is the heralded Black Canary, master assassin and eventual League leader. As Dinah battles psychic manipulation and endures genetic tampering and martial arts training, Oliver struggles to survive on a diet of birds and fish, using a makeshift bow and arrow to hunt. Queen is eventually rescued to great fanfare, and as a final test the League of Assassins orders Lance to assume the mantle of Black Canary and kill her former lover. Naturally the power of love overcomes the League's brainwashing, and the new Green Arrow joins Black Canary in destroying the assassins - or at least putting a dent in their plans. Luthor and Wayne note the appearance of two new costumed adventurers...
Light comedy Zatanna introduces the Mistress of Magic as the world's first closeted super-hero. While the world sees her as just another stage magician, Zatanna is in fact in tune with the ancient mystic arts of Atlantis and Paradise Island. While she wishes she could just enjoy her career as an illusionist, growing extra-dimensional threats force her to take a more active role in defending civilization from ruin. A brief post-credits scene features a "meet cute" between Zatanna and Bruce Wayne, establishing a possible spark of romance between the bubbly magician and the brooding hero...
Man of Tomorrow, the second Superman film, establishes a growing rift between Clark Kent and Lex Luthor. As Kent juggles the responsibilities of his dual identities, Luthor becomes increasingly obsessed with Superman's growing fame and public adulation. While Superman, warned by Green Lantern, battles intergalactic menace Brainiac, Luthor quietly assembles a secret society of super-villains to end what he sees as the meta-human threat once and for all...
In Suicide Squad, we learn that it's not just Luthor who's worried about the free agency of powerful figures such as Superman, Batman and Green Lantern. Amanda Waller assembles Task Force X, a Suicide Squad of mutants and covert operatives who plan the ultimate caper: learn the weaknesses of each hero just in case those heroes ever turn against humanity. But when Waller learns of a larger threat, she's forced to change missions midstream, putting all of her operatives at risk. Will any return from a certain suicide mission...?
Finally, in Justice League of America, Luthor's secret society, guided by future intelligence from Professor Zoom, targets each League member for assassination. But silent partner Bruce Wayne deduces the plan and assembles the heroes to fight Luthor's society, the League of Assassins, Professor Zoom and Task Force X. Our heroes will have to learn to work together...or die trying.
There you go, Warner Brothers. I'd buy a ticket to each film and even make Sylvia come with me, and I'd even buy the ultimate Blu-Ray special edition box set of all the films. Get cracking!