Reasoning:
Dr. Doom is a good fit for a Luthor counterpart - and in fact, Luthor's Squadron Supreme counterpart Master Menace has a very strong Dr. Doom flavor. They're both high-tier mad scientists who are, at heart, horribly petty and vain. Of course, the occasional more morally ambiguous version of Doom contradicts this.
Dr. Octopus also fits the vanity and pettiness, combined with scientific brilliance. That said, Dr. Octopus is more someone trying to be Luthor and failing.
Green Goblin is the person who has caused personal tragedy to his given hero, as well as a colorful and ever-smiling villain with severe mental problems. Like Dr. Octopus vs. Luthor, there's a distinct manner in which Marvel handles it more for pathos.
Mandarin = Ra's for simple reasons of both being different derivations of Fu Manchu, and both having a history of trying to destroy modern technological society.
Magneto = Sinestro because both are well-intentioned villains who have switched sides several times. Dr. Polaris is a Magneto counterpart on powers alone, but not a very good fit in terms of role.
Red Skull is a little hard to find a significant counterpart for...DC has a few Nazi supervillains around, but none as prominent as the Skull is.
edited 20th Aug '13 6:35:40 PM by TheEvilDrBolty
Lex Luthor —_— The Kingpin, at least until the latter is outed as a criminal he was pretty much untouchable and at one point secretly controlled most of the United States Of America.
The Joker —_— Scarecrow, at least his more recent characterizations, which is just as well, Joker was not always the crazy murderer he is now. Sabertooth works too, excepting the fact he is a mutant.
Ra's Al Ghul —_— Sebastian Shaw, though the hand is a better analog to the league of assassins they are both old rich guys trying to rule the world.
Sinestro —_— Morph weapon, self righteousness, defection, later spawns lots of similar characters? I'm thinkin Venom.
The Red Skull —_— Dr. Poison, antiquated supporters of the Axis powers and all
Magneto —_— Dr. Die Hard, deliberate example with a little bit of Professor X thrown in
Doctor Doom —_— That one is pretty easy, the Extremists were a team of deliberate Marvel knockoffs though Lord Havok is not as successful
The Mandarin —_— Egg Fu?
Modified Ura-nage, Torture Rack

Simply put, which villains from DC comics are the equivalent to which Marvel Comics villains?
Examples:
Who are the Marvel equivalents for: Lex Luthor
The Joker
Ra's Al Ghul
and
Sinestro
Who are the DC equivalents for: The Red Skull
Magneto
Doctor Doom
and
The Mandarin
edited 20th Aug '13 5:52:00 PM by srebak