This.Sean Steele said:The term Mary Sue means to many things to too many people and thus is meaningless.
For example, I would say that identifying POPULAR Mary Sues, like Bella Swan, is an inherent contradiction.
While she fits the most simplified definition in that she is an overtly perfect heroine, she doesn't fit the original PURPOSE of the Mary Sue tag in fanfiction communities, that was a way to warn amateour writers that they are going off on a tangent with blatant self-insertions that's petty wish fulfillments would bore everyone else.
That obviously doesn't apply to Twilight, or to any of the franchises listed above, since they already have huge fanbases that don't consider them too boring.
Most of those are not really writer avatars, but audience avatars, that is a completely different thing. If you start bludgeoning general escapist characters with the term "Mary Sue" just for being too perfect, you are no longer complaining about bad writing, just forcing your random literary theories, about how protagnists should act, on others.