Hal Jordan was dead, and the Last Ring was taken up by Kyle Rayner. "You will surpass him," the King of Dreams told Kyle, in Morrison's JLA.
Oliver Queen was dead, and the mantle of Green Arrow was taken up by his lost son Connor Hawke.
Barry Allen was dead, and Kid Flash had to live up to his legacy.
Jason Todd was dead, and Tim Drake was determined to prove himself a better partner for the Batman.
Superman was dead (briefly) and it took 4 people to fill in for him. I could go on.
Where are they now?
Kyle Rayner, off in space somewhere, while Hal Jordan, back from the dead, is the focal point of the GL mythos again.
Connor Hawke, no longer able to shoot an arrow but now gifted with a healing factor he got from being spliced with DNA from Plastic Man. Meanwhile, Oliver Queen, back from the grave, married the girlfriend he had in the 70s and is the one true Green Arrow.
Wally West, aka Kid Flash, had his book cancelled, was replaced by Bart Allen, who died, replaced by Wally again only to have his book cancelled a second time. Barry Allen, back from Speedster Heaven, is the one true Flash back in Central City.
Tim Drake was replaced by his girlfriend who was capriciously killed and later unkilled. Jason Todd, who was capriciously killed in the 80s, is now unkilled.
John Henry Irons spends less time as a superhero and more time as a replacement for Professor Emil Hamilton. Kon-El Kent was killed off and thanks to a lawsuit couldn't even be called Superboy when it happened, the Eradicator only shows up on Kryptonian High Holy Days, and the Cyborg Superman is...um, something happened to him in the Sinestro Corps War but I can't be bothered to remember what.
I could bring up Thunderstrike, Ben Reilly, Danny Ketch, whatever the hell Rhodey is now, The Manhattan Guardian, the v3 and v4 Legions, and whichever Doom Patrol is in continuity this year, but it's late.
The shared universe of Marvel and DC have gotten very good at the illusion of change, but in the end it all boils down to what the writer liked reading when he was 12. Because that's what you're going to get on the page. Marvel's brought back every 70s character from Angar the Screamer to Zzaxx, and all the Superfriends killed off in the 80s and 90s are running around again. I can see the 90s revival coming on the horizon--Darkhawk has had TWO #1 issues this year and it's only April.
Darkhawk. Sheesh.
The "growth" you're talking about is nice while it lasts, but it doesn't stick. Only Dick Grayson seems immune, but the year's not over yet.
Meanwhile I eagerly await Charles McNider/Vic Sage/Karate Kid/Ted Kord: Rebirth, The Kraven Clone Saga, and the All New All Deadly Brother Power the Geek.
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Oh shit they did that one.