I'm not going to cite examples. Frankly, I used to read a LOT but haven't in recent years. I DO score writing on tests taken by school kids though, and yes, there have been some examples of great writing by kids. Some have been at least as good, if not better, than current professional writers.

The thing that does it for me is perhaps the same thing that works in art or music. The writing is effortless. The writer OWNS the language, and skillfully uses it to lead the reader somewhere WITHOUT the reader becoming conscious of being led. If the effort shows (ooh - look at the big words I know and all the complicated sentences!), the writing is difficult to read.

Writing I don't like and think is not good is similar to a minimalist painting or a song with too many words and little meaning. Those things are meant to make you stop and think "oh, how clever" - about the artist. I'd rather consider the work itself and think "oh, how beautiful" or "how powerful/sad/right/etc."

The really, really bad stuff makes you think "huh?"