The Mary Sue Misapplication

Mary Sue (n): An idealized, practically perfect character in fan fiction, almost always created as a way for the author to insert themselves into their favorite fictional universe. Mary Sues often upstage the universe's established characters, winning their respect and sometimes even their romantic interest.

Believe it or not, in the early years of Star Trek fandom the fanbase was predominately female. In fact, without the passion of the mainly-female fans who organized conventions and published fanzines during those years when Star Trek was nothing more than a cancelled TV show, we never would've gotten 13 feature films and five spinoff television series. Kind of makes those dudes who accuse female fans of being "fake geek girls" look like even more voluminous douchebags, doesn't it?

Anyway, fanzines were fan-published magazines that contained fanfic, poetry, and essays--the kind of things you see on the Internet today. In the second issue of the Menagerie fanzine published in December 1973, author Paula Smith coined the term "Mary Sue" to describe the type of Star Trek fanfic featuring the youngest officer in Starfleet history who comes aboard the Enterprise and instantly wins the admiration (and possibly romantic affections) of Kirk, Spock, and McCoy, even as she upstages them all by effortlessly saving the day with her brilliant genius. It goes without saying that a "Mary Sue" character could also be male, it's just that the vast majority of fanfic authors in that first decade of Trek fandom were female and therefore the nickname that was coined for any wish-fulfillment author-stand-in character was a female one. At least it should go without saying. In actual practice, female fanfic authors quickly found that any female character they created, no matter how well-drawn and realistic, was dismissed by male readers as a "Mary Sue". But it gets worse:

Until pretty recently, I never heard the term applied to any characters outside of fan fiction. The only exception I can think of was Star Trek: The Next Generation's Wesley Crusher, (a youthful super genius who often improbably saved the day and who Gene Roddenberry admitted was somewhat based on himself). But then a funny thing happened. Female protagonists started to show up with increasing frequency in sci-fi and fantasy, and suddenly male fans were loudly denouncing every one of them as a "Mary Sue".

Case in point: Rey from The Force Awakens. Google "rey mary sue" and the number of results is depressingly more than zero. But why? The main reason the (always male) proponents of this argument give is that she has "unrealistic abilities". Well duh. Most every story you love features a character with superpowers or super awesome fighting skills or genius-level intelligence that helps them solve complex mysteries or invent incredible things that defy the laws of physics. News flash: those are all unrealistic abilities. Here are some other reasons why Rey cannot by definition be a Mary Sue:

1. The Force Awakens is not a fanfic. Maybe it's not exactly the Star Wars Episode 7 you imagined in your head after the disappointing prequels, but the fact is that The Force Awakens is an official entry in the Star Wars canon. and one of the things it's designed to do is introduce a new generation of characters like Poe, Finn and especially Rey. 
2. Rey is not an author stand-in. The Force Awakens was written by Lawrence Kasdan and J.J. Abrams. I'm 99% sure neither of those guys is a young woman, and I can't prove it, but I'm fairly certain none of them fantasizes about being one. At least it's never come up in their other work.

Since basically forever the entertainment industry has been catering to white guys like me by giving us heroes who look like ourselves. But now Hollywood is slowly starting to realize that women have money, too, and they're more likely to spend it on movies where the characters who look like them are treated like real people and not just a talking prop or a trophy given to a male hero for saving the day. Only an idiot would feel threatened by this. Or Max Landis. But I repeat myself.

So knock it off, guys. Stop trying to disguise your sexism as thoughtful artistic criticism. Your genitals aren't going to fall off just because traditionally male-dominated franchises are starting to get more female heroes.