Salvaged Story: This arc served to resolve the various contradictory appearances of Brainiac in Post-crisis continuity by by streamlining them into proxies of the real Brainiac, while returning him to his Silver Age roots as a Planet Looter who collects bottled cities including Kandor.
The character
Adaptation Displacement: Most people who know about Brainiac are more familiar with his evil AI incarnation from the cartoon than they are with the earlier comic book incarnations. This is most likely the reason it has become a frequent Ret-Canon.
Love to Hate: Brainiac is one of the few villains who can go toe to toe with the Man of Steel. His cold desire for Knowledge at any cost and status as the thematic Evil Counterpart to Superman make him one of the most well liked members of the Superman Rogues Gallery.
Mainstream Obscurity: Brainiac was so ubiquitous and popular in the Silver Age that his name became slang for intellectual and introduced a word in the cultural lexicon, but his cross-media appearances has prevented him from being as famous as other villains. He has yet to appear in a single Live-Action film version of Superman (which have had Lex Luthor and General Zod taking turns as the main villain for seven films now) and his most well known appearance, the DC Animated Universe take, is different enough from his comics that they make newcomers confused about the two versions.