John Byrne's ambitious twelve-issue, limited series three-quel to Superman & Batman: Generations and Superman & Batman: Generations II.
Here, Byrne - known for his work on X-Men with Chris Claremont; Crisis on Infinite Earths follow-up Legends; Superman re-boot, The Man of Steel; Spider-Man re-boot, Spider-Man: Chapter One; X-Men: The Hidden Years; the Dark Horse creator owned Next Men; as well as work on Captain America, Doom Patrol, Fantastic Four, The Incredible Hulk, The Indiana Jones Adventures, Justice League of America, Lab Rats, Namor, The Sub-Mariner, She-Hulk, Space: 1999 and Star Trek - spans the ages here with Kirby's Fourth World New Gods and the Legion of Super-Heroes.
This is the third and final Elseworlds "imaginary story", where Byrne ages Superman, Batman, and in turn the rest of the DC Universe. Generations III spans from the days of Superboy in 1925 to 2925.
The subtitle to Generations 3 is now, "An Imaginary Series".
Collected in Superman & Batman Generations Omnibus.