Trying my best to put this into an extremely simplified format. This is basically the post-Crisis/New Earth inspired Elseworlds I would write it if DC called me up tomorrow. I wouldn’t want to wade in the Nu52 and start retconning things around to suit me, even if I could get away with it–there’s been quite enough of that from Messners Didio and Johns. I’d rather just tell a damn good story in its own continuity and have that continuity as close to fan-preferred status as possible. Please feel free to debate and comment, I’d love to hear any feedback.
The Zeroth Generation: WW2 and the Justice Society of America, among others. Through various circumstances, a number of these heroes find themselves in stasis to reawaken in the more proper Age of Heroes.
The Lost Generation: Scattered superheroes between the end of the Zeroth Generation and the beginning of the Age of Heroes. Not many are of note; the frequency and fame of these heroes is more akin to guys like the Viking Prince and Jonah Hex pre-Zeroth Generation. Someone’s putting on tights, but it’s largely unremarkable.
The First Generation: (15-10 years before present day) The Age of Heroes begins with Superman debuting in Metropolis, having wandered the globe on a Quest for Peace (heh) since his high school graduation. Urban legends spread of the Batman of Gotham, while Diana leaves Paradise Island for Man’s World. In short order, the rest of the ‘Big Seven’ show up: Green Lantern, the Flash, Aquaman, and Martian Manhunter. Over this five year period, the Justice League is formed, then expands its ranks. Many of the heroes acquire sidekicks, who themselves form the Teen Titans. This era roughly corresponds to pre-Crisis comics, John Bryne’s initial Man of Steel comic, Miller’s Batman: Year One (and ensuing stories), the Happy Harbor and Satellite Era of the Justice League, and George Perez’s Wonder Woman stories*. Most heroes are somewhere in their twenties, while sidekicks are adolescents (let’s say Dick Grayson becomes Robin age twelve-ish).
The Second Generation: (10-5 years before present day) The Justice League transitions into the ‘Bwa-Ha-Ha’ Justice League International, the Teen Titans become the New Teen Titans, the Suicide Squad is formed. New heroes are born, following the example of the First Generation. Old sidekicks graduate to higher statuses (Dick Grayson becomes Nightwing, Wally West becomes the Flash, Donna Troy becomes Troia) and new sidekicks take their place (Jason Todd becomes Robin II). This era roughly corresponds to post-Crisis comics of the eighties and early nineties, starting from the Legends miniseries and continuing onward. Adult heroes are entering their thirties. First generation sidekicks are in their teens and very early twenties (Dick Grayson was about 18 and in college when NTT started).
The Third Generation: (5 years ago to present day) The latest generation of heroes and sidekicks arrive, from Tim Drake/Robin III to Cassie Sandsmark/Wonder Girl II to Connor Hawke/Green Arrow II. The Big Seven return to the Justice League, building a new base on the Moon known as the Watchtower. Young Justice is formed. This era roughly corresponds to the post-Crisis comics of the 90s and early 00s, including Grant Morrison’s JLA. It runs until Identity Crisis/Infinity Crisis. Adult heroes are in their thirties and forties (Bruce and Clark have some white hairs). First generation sidekicks are solidly in their twenties.
There’s also a Fourth Generation, obviously, covering the late Aughts and Tens which we’re in now, introducing new heroes/sidekicks like Harper Row, Jessica Cruz, and Jonathan Kent. However, as this period also leads into Flashpoint and strongly features the replacement of legacy heroes with their predecessors–Barry Allen retaking the Flash mantle from Wally West, Hal Jordan doing the same to Kyle Raynor, etc.–I prefer not to acknowledge it in favor of setting my tale within Third Generation and continuing that thread. Also, the new characters I mentioned are largely still being ‘field-tested’ by their creators, so for my purposes, I’d prefer not to give ‘my take’ on characters who largely aren’t established enough for me to give them a take.
I also reserve the right to screw around with canon a bit for the sake of storytelling. So, for instance, in mainstream canon, Barry Allen would die in CoIE right between the first and second generations and by the Third Generation Wally would be married to Linda and starting a family. Because I want to write a love story between them, I put off Barry’s death until the third generation, so Wally has only been The Flash for a few years and is just now meeting Linda. That gives us quite a few stories that strictly speaking didn’t happen, but it’s an AU anyway, and at least I’m not making you read about Barry fucking Allen fucking Patty fucking Spivot.
*Technically, those stories took place during the Second Generation, five years after Superman and Batman had debuted, but no one really likes that retcon and it totally fucks up Donna Troy being a Titan. So… Hypertime.