After that, what are the actual reboots? "Zero Hour," obviously, but that was less a reboot and more a tinkering. The only things that really changed due to Zero Hour were Batman's urban legend status, Hawkman's confusing complexity, and what the Legion of Super-Heroes was like.
"The Kingdom" is the next one that deserves mention. It didn't reboot or retcon anything; it just made the multiverse a thing again through the magic of Hypertime. Now, every story that DC published took place in a variety of divergent universes. Which was kind of already the case, "The Kingdom" just canonized it.
"Infinite Crisis" was the next "reboot" (commentators tend to lump "Identity Crisis" here because it has the word "Crisis" in the title, despite not doing anything to the timeline), making a few cosmetic changes the same way that "CoIE" did, but more becoming the scapegoat for the sorts of changes that occur naturally in a century-spanning serialized shared universe. And we'll get to that again below. The biggest impact "Identity Crisis" had on continuity was through restoring the multiple Earths-style multiverse, paring the number down from ∞ to 52. These weren't the old Earths restored (as JSofA would go to show) but new Earths that, in some cases, bore resemblance to some of the numbered Earths from the pre-Crisis era. And in most other cases, bore resemblance to various Elseworlds titles like "Gotham by Gaslight" and "Red Son." We saw some tweaked origins and such post-IC (notably in the "Look, Up in the Sky" Superman arc), but nothing particularly major.
Post-Infinite Crisis, there really hasn't been another attempt at rebooting or mass-retconning. People point, again, to "Final Crisis," because of the "Crisis" title, but despite the story's heavy involvement with the multiverse, there's nothing there to really rewrite existing DC history.
Which isn't to say that such rewrites haven't occurred. The "Secret Origin" titles--running through "Green Lantern" and the Superman miniseries--have both made tweaks, both major and minor, to those franchises, but without a universe-spanning justification ("Superman: Birthright" did the same, ten years back). This is certainly cause for some confusion among the long-time fans (did Ron Troupe and Lucy Lane have a son or not? If the 'new recruits don't have Lantern badges' was a thing when Hal joined the Corps, then why did they bother introducing it as a new idea in "GLC: Recharge"?), but they've generally been matters of nitpick-level importance, not serious detractions.
And as comic fans, we should be used to that sort of thing by now, because they happen all the time. As I mentioned above, Marvel gets a free pass on the "universal rewrite" thing, but not because the details never get rewritten. Instead, Marvel is in a constant state of flux with respect to those details, such that Tony Stark was originally a POW in Vietnam, then the Gulf War, now Afghanistan. Reed Richards and Ben Grimm no longer met in World War II, and were no longer racing against the Russians to be the first on the Moon. The details get smoothed out, ignored, and rewritten periodically at Marvel, such that the "starting point" of the Marvel heroes is a sliding scale, always creeping toward the present, always kept a constant-but-unclear distance in the past.
Which is not to say that they haven't had harder reboots too; "Heroes Reborn" was a specific attempt at just that, as was "Spider-Man: Chapter One." "One More Day" sits somewhere in-between on the Sleep Number scale of superhero reboots.
Of course, Marvel has had one hard universe-wide reboot, though they tried to have their cake and eat it too: the Ultimate Universe. It's frankly a harder reboot than anything that DC has done since "Showcase" #4, but they just shunted it all to a side universe. And I think the Ultimate universe (along with other hard-reboot examples like "Man of Steel" and "Spider-Man: Chapter One") shows some of the pitfalls and problems with hard, line-wide reboots on the whole:
- The Best Laid Plans: Generally, the stated goal of a hard reboot is to jettison the decades of confusing history and continuity that might make the title a daunting read for the casual fan or new customer. The logic is that this confusing history piled up over a long period of time with no overarching plan, so an overarching plan will prevent the new history from being so confusing. Contradictions and continuity errors and tangles will generally fail to exist, because everything is planned in advance.
But even the best plans don't account for everything. For the "Man of Steel" reboot, for instance, the biggest problem was first addressed in "Superman" (vol. 2) #8: if Superboy never existed, then who inspired the Legion? The consequence of a hard reboot in one corner of the shared universe meant that a different corner was suddenly far more complicated, as it required a tangled mess of pocket universes and counterparts and so forth.
For the Ultimate Universe, the problem came in "Ultimate Marvel Team-Up," which introduced a bunch of characters who would later be reintroduced...and totally different. So some of "UMTU" became canon, other bits didn't, and continuity tangles were born.
- Historical Inertia: Characters, one way or another, develop, despite the best efforts of the status quo. A hard reboot, setting everything back to the beginning, thus comes with a lot of the baggage it was trying to jettison: mainly, how these familiar characters will grow and develop. Some developments are necessary and obvious: doesn't matter how much characterization or how many ponytails you give Uncle Ben, we all know he's going to die. That's his purpose as a character.
But that sort of thing carries further. Take a Robin reboot for instance. Let's say DC resets things all the way back to the original Dynamic Duo. There will always be that tension hanging over Dick Grayson, about whether or not he's going to leave and what his eventual grown-up trajectory will be. Readers will always be waiting for Nightwing, and writers will always be acknowledging Nightwing in some fashion--either by trying to set it up as an eventuality or trying specifically to avoid it. Either way, Nightwing--and now, Batman--will be the shadow hanging over any young Dick Grayson story.
And frankly, it'll probably take them less time to get there. The first time around, it took 45 years or so for Robin to become Nightwing, and if we had to do it all again, I doubt it would take more than ten. "Nightwing" is seen as the trajectory of Dick Grayson's story, and everyone from fans to writers is going to be expecting it to happen.
As a less hypothetical example, consider Supergirl. It took 21 years after Superman's debut for them to create a Supergirl; after the reboot, however, even given a "no more Kryptonians" edict, it only took two. Consider that the Ultimate Universe has existed for about eleven years, but has already had everything from the Death of Gwen Stacy to Venom and Carnage to the Clone Saga, compressing some forty years of significant Spider-events into a quarter of the time.
Sure, they aren't exactly the same stories. This time, Supergirl is a superpowered protoplasmic clone of Lana Lang from a pocket universe, this time one of the Spider-Clones is a girl. But the changes are mostly cosmetic, mostly detail-based. The same basic story is happening again, either because it's seen as inevitable (the death of Gwen Stacy), because it introduces useful or popular bits of the discarded continuity (Supergirl's return) or because the new writer wants to pay homage to an old story, or "do it right this time" (Clone Saga). Which brings us to the next point:
- Meet the New Boss, Same as the Old Boss: Continuity reboots are not a way to tell new stories. You don't need an excuse to tell new stories, and new stories are perfectly possible within the confines of an established continuity. Want to tell a story that ignores or contradicts some inconvenient continuity point? Do what people have done since time immemorial: ignore or contradict it. That's what No-Prizes are for. Or find a way around it--make the story a flashback, set it in the past or the future, add a little "This story takes place before events in" caption. There are plenty of ways to tell stories that aren't hampered by the long history and shared universe even when you're in a shared universe with a long history, and various writers have been very successful in recent times by treating those long histories as smorgasbords built to pick and choose the best bits from.
Of course, there are ways that continuity hampers what stories can be told. Writer wants Character A to team up with Character B against Character C, but Character B died before Character C debuted, or something. There may be editorial red tape preventing Character B from being resurrected, and the story has to be reconsidered somehow. I don't necessarily see that as an argument against continuity; it's more an argument against killing characters. Killing useful, interesting characters is like breaking the toys in the toy box; it reduces the number of games you can play, until someone takes the time and effort to fix or replace the broken toys.
The only real counter-example I can think of is Neil Gaiman's "Legend of the Green Flame," a story that was famously filed away because part of it hinged on Superman and Green Lantern knowing each other's secret identities, which wasn't the case post-Crisis. I'm sure other stories have fallen into the file like this one, for similar reasons, but it's hard to catalog stories that were never told. The problem with using "Legend of the Green Flame" as an example of how continuity can limit what stories can be told is that it was eventually published anyway, outside of continuity (though it didn't matter by that point), and that the problem which prevented its publication wasn't continuity, but a continuity reboot. The story would have been completely fine just a few years earlier or later; rebooting continuity was what caused the problem.
No, the biggest reason for doing a reboot is to retell familiar stories again. Those retellings are, of course, going to be different in various ways, but "the origin of Firestorm" is going to have similar attributes whether it's about Ronnie Raymond and Martin Stein in college or Ronnie Raymond and Jason Rusch in high school. And eventually, one way or another, historical inertia is going to carry those rebooted characters to familiar ground, whether or not it's in new and slightly different ways. The baggage isn't lost, it's just shoved to the back of the closet.
- Worst of Both Worlds: That's the biggest problem with reboots: you lose the smorgasbord of past stories to pull interesting and fun details from and you leave that historical sword of Damocles hanging above every writer's head. The best writers will use the history as a guide or inspiration, using the unwritten history to inform the story one way or another. The worst writers will use it as a crutch, a way to tell the same stories that have already been told, but with minor cosmetic changes to make them fit the new status quo.
Which is not to say that there's no innovation, but I think it represents a step backward. Consider the Superman/Lois dynamic. We had fifty-eight years exploring every aspect of their classic two-person love triangle, which also formed the basis for every superhero relationship that followed (and that's ignoring all the flashback stories, out-of-continuity stories, and everything else since the marriage in 1996). Conversely, their actual marriage remains largely unmined for story opportunities. Undoing it would have the unfortunate result of leaving everyone with the (reasonable) assumption that they'll eventually get back together, and leaving the writers and readers in very well-explored territory. The focus of the tension will have shifted; in the Silver Age, it was "will she ever figure out his secret?" "will Superman ever settle down?" "will Superman choose between Lois and Lana?" Post-reboot, the tension is "when will they finally get back together?" "when will she learn his secret?" The former is the kind of tension around which you can build satisfying stories and conflict. The latter is the kind of tension around which you can build "Moonlighting."
I just think that this whole kerfuffle is missing the forest for the trees. It might be true that comics are inaccessible to new readers, but wiping out all history--or worse, wiping out some histories and not others--doesn't make things any more accessible. What makes comics accessible to new readers is getting them out of the comic shops. Unless someone is already interested in comics, they're unlikely to enter a comic shop. Unless their comic shop is one of the really good ones, it's unlikely that the comic shop will have a welcoming atmosphere to new readers, or accommodating to the kinds of questions that new readers have. The future of comics lies in bookstores and the Internet and other places where new readers are more likely to be than insular comic shop clubhouses. The future of comics lies in attracting new writers and new artists with new ideas.
That should be obvious, from the success of "Superman: Earth One" in the mass market, and from the basic facts of most current comics fans. Think back, folks: where'd you get your first comics? I bet it wasn't at a comic shop. I got mine from newsstands and grocery stores and He-Man toys and my mom's yellowing collection. That led me to the weird assortments they sold in Sears Christmas Catalogs and grab bags at toy stores, and only after getting hooked on all that did I get to a comic shop.
Instead, DC's lesson from "Earth One" seems to have been that people want to read about younger characters and origin stories. And some of that may be true, but there's only so many ways and so many times you can tell an origin story. And it looks like we'll be seeing more such stories come September. I just hope the plan is bigger and better than it seems at the moment.
And I really hope Green Arrow's not in the Smallville costume for very long.
By the way, I'm totally aware of how many sentences in this start with "and" or "which isn't to say." Consider it a stylistic choice. As in, I stylistically chose not to do any editing on this meandering post.