What's considered well-written quote?

So, there's been a discourse going around Twitter for months about poorly written prose from fan fiction and how it's affecting people's literacy in contrast to well-worded prose from actually acclaimed literature. I'm not a native English speaker and to be honest, sometimes I find quotes from famous professional writers having almost the same quality as those from eloquent fan fic. I want to ask what's good prose and whatnot. (I would appreciate examples of each)
This place isn't the best to discuss literature but anyway—