^ Actually, that Doom-Galactus story in Fantastic Four: World's Greatest Comic Magazine was published in 2001-2002. It was one of those untold tales that is in-continuity in Marvel's past (Reed erased the events form everyone's memory except himself and Watcher), but is a very recent story:
^ The story had never been told until 2001-2002. It was 12-issue limited series homage to Stan Lee and Jack Kirby. Several writers and artists contributed to the idea, headed by Erik Larsen. As you can see from the scans, all the writers emulated Lee's writing (Erik Larsen, Chuck Dixon, Tom Defalco, Jeph Loeb, Kurt Busiek) and all the artists emulated Kirby's art (Larsen, Jae Lee, John Romita Sr., Keith Giffen, Bruce Timm, Ron Frenz).
They explain in the book that the events chronologically take place before Fantastic Four #100. The reason why nobody remembers these events taking place, is that Reed restores all the damage done and erases everyone's memories except his and Watcher's at the end of the tale. So it's not an old comic per se (when writers still hadn't decided how powerful Galactus was). It's just done in the classic style and set in the past.
What I find very strange in the comic, is Doom's various comments regarding the cosmic cubes powerlevel in comparison to Galactus and how it actually performed against him, it's a bit like the Infinity Wars incident where Galactus breaks the containment the 5 CCU had made for Eternity and Infinity, yet shows that he can't defend himself completely against a attack from the very same CCU. That have lead me to believe that the powerlevel Galactus have against the CCU, is pretty much as the writer wants it to be, while his powerlevel against the CCB is more solid.