Professor X and Magneto are based on Martin Luther King, Jr. and Malcolm X.
This excellent piece on Screened highlights a succinct quote from Uncanny X-Men writer Chris Claremont:
The X-Men are hated, feared and despised collectively by humanity for no other reason than that they are mutants. So what we have here, intended or not, is a book that is about racism, bigotry and prejudice.
Charles Xavier’s character is defined by a pursuit of mutant rights and equality via peaceful means and encouraging acceptance, while Erik Lehnsherr takes a more militant approach toward the same end. If you read the MLK and Malcolm X quotes in that Screened piece, the author astutely points out that these seem like the very sentences that would have been uttered in X-Men comic book panels. Michael Fassbender claims the dynamic between Martin Luther King, Jr. and Malcolm X served heavily as inspiration for he and James McAvoy’s rehearsals for their roles in X-Men: First Class.
Peter Parker and Johnny Storm meet at the Statue of Liberty every Christmas to exchange presents.
And sometimes The Human Torch gives the gift of skywritten festive messages to the whole town.
Richard Nixon was a supervillain.
A 1974 Marvel Comics storyline featured Captain America battling a clandestine group called The Secret Empire, while simultaneously defending his image from a smear campaign engineered by a group called the Committee to Regain America’s Principles, or, as you might have already deduced, C.R.A.P.. Upon defeating the organization, Cap unmasks the mastermind, then-president Richard Nixon.
Rather than face the consequences, Nixon commits suicide, and is replaced by a double that is then allowed to resign after a government-crafted Watergate scandal, which was created as a way to explain the end of Nixon’s presidency. Steve Rogers is so disgusted by the entire mess that he decides to leave the mantle of Captain America for a time, although, like any readers who may have left for the same reason- this is comics, so we know they came back (as did Rogers).