Since the "Rey is a Mary Sue" meme persists on even in this thread, I present to you:
The Grand List of Rey's Failures and Personal Flaws
- Spent most of her life living in utter poverty, only managing to not starve.
Maybe you haven't really looked into what typical "Mary Sue" traits are considered to be. Having an exceptionally tear-jerky backstory is one of the biggest ones. An impoverished childhood and nearly starving is core "Mary Sue" type stuff.
http://tvtropes.org/pmwiki/pmwiki.php/Main/CommonMarySueTraitsShe speaks several languages fluently.
http://starwars.wikia.com/wiki/ReyRey also had a computer display from an old BTL-A4 Y-wing assault starfighter/bomber that she used to learn alien languages
Most Sues have an unusually Dark and Troubled Past. It's often used to create a Sympathetic Sue, but any type of Sue can have one. Such backstories never actually factor into the story; they're just casually dropped into the narrative to draw attention to the character and let her Wangst (usually out of proportion to how bad it really is). Most authors tend not to research such tragedies and their effects, which breaks the reader's Willing Suspension of Disbelief.
Relatedly, she will often have a tragic family life. This could involve Parental Abandonment or orphanhood, and whichever parental figures she has are often abusive, putting her squarely into Cinderella Circumstances. Darker fics will often have Rape as Backstory. She might be the Black Sheep who's so smart and talented that the rest of her family fears and abuses her — or she might be the White Sheep who's the only redeemable member of her otherwise evil family. Regardless, this backstory will never actually hold Mary Sue back from anything she wants to accomplish.
She will always be better than the canon characters, regardless of what canon has established they can do or whether it makes any sense. ... Her skills will often be unrealistic within the story's setting. She can be a master of a martial art that she should have no way of learning
This doesn't need elaboration
Typical Mary Sue storytelling is about how
everything was against you, yet you won because you had the "special stuff" that nobody else had. Them hammering how
terribly poor "nothings" her parents in the current movie
increases her Mary Sue level. What would be
less Mary Sue is if her parents turned out to be completely average suburban types who
didn't live a horrid life and abandon her as an orphan. This is actually what makes Luke
less of a Mary Sue, and more relatably human. He had a fairly uneventful normal farm-boy existence, with they typical teenage gripes and complaints - but
then tragedy strikes, throwing him out of his normal life. It's relatable, because
losing your parents is a relatable thing. Rey's upbringing - abandoned as a tiny kid (she had to have been about 6 years old, going off everything she learnt before she was
10 years old according to the Wookiepedia entry) in a galacitic rubbish dump and surviving by scavenging while somehow miraculously bootstrapping yourself into learning
every skill better than anyone else does - is not believable, it's farcical.
Another key Mary Sue trait is hob-knobbing with all the "canon" characters, no matter how implausible that is. Her ending up meeting Han Solo, Chewbacca, Luke Skywalker and Princess Leia is the type of thing
bad fanfic writers doing self-insert fiction (which was the
original Mary Sue critique) would do.
The rest of the original Mary Sue traits mainly involve breaking previous canon with the types of abilities the character has. She flies the falcon better than Han Solo, masters the "jedi mind trick" instantly, and can hold her own as a
rookie against trained Jedi masters, while also basically doing the force levitation trick when needed, at a level Luke wasn't even able to get to until his third movie.
Also, Mary Sue characters often develop some sort of deep emotional bond with more "canon" characters despite they themselves being self-inserts shoe-horned in.
Rey, being a character completely unrelated to the-canon, but having a deep connection with Han and Leia's son who's the "troubled dark emo type", while basically inheriting the Millennium Falcon from Han Solo,
and being the sole heir to the Jedi legacy via training with Luke - that's all by the book Mary Sueism.
What makes her a Mary Sue is the fact that other that her basically
none of the other characters have really developed much of any sort of relationship with any of the canon characters, while she has with all of them. The only one is Poe, and Poe's connection with Leia is more or less her telling him off for failing (e.g. the opposite of being a 'Sue).