What makes a novel "a classic?"

This is a hard question to answer. I've began typing about four times now and have erased everything. What does make a classic?

For one, there has to be an impact that a novel makes. Whether at its time of publication, or years later; there has to be a stir. And I think there has to be some controversy. That would only make sense, right? When has anything ever been a "classic" if its been either completely loved or completely hated?

And, a classic has to be well-written. Meaning, Twilight can go down in history as the most overrated pieces of crap ever written an extreme outburst in pop culture, but the fact remains that the writing is mediocre and therefore, it can't be a classic. And that's where Harry Potter is questionable, because the first book certainly isn't a literary masterpiece, nor is the seventh, but with each book the writing quality certainly increases. But the story is so much better and the characters are so much more likable and well-developed, and JKR doesn't describe vampires as 'glistening like a thousand diamonds,' or whatever that crap was. But I don't know, I'm clearly biased.

Anyway, I think what Brenda said was true, too. The story has to have something universally appealing about it. Or, rather, it has to have something that influences future writings. Romeo and Juliet was definitely the first of its kind, and now look at how much ~forbidden love~ (ahem) there is in books, T.V., movies. There has to be a first-of-its-kind type of aspect to make something a classic.

Then of course there is the time issue. One can't really say that a new release is a classic, can they? I mean, I guess one could predict that it will be a classic, but there probably has to be between 20 and 50 years after the book is released to be able to firmly say if it's a classic or not.

Aaaaaaand all of this indecisiveness is making my head hurt.