Good writing
For me, good writing is sompletely independent of story and character. It's words and sentences and paragraphs you would enjoy reading, even if there were no story and no characters. It sings, it hits you with unexpected twists and turns. It's all about language and new ways of saying old thing.
Great writing goes a step further. Great writing is a contradiction. . .it's both ever-present and completely invisible. It sings silently, filling the back of your mind, hums in your subconscious, but never, ever gets in the way of story and character.
Story and character obviously outweigh good writing for publishing purposes, but for story and character to last, to be read for pleasure generatons later, a novel really needs good story, good characters, and good, if not great, writing.
But defining it? I'd say the best way to do this is to read the writers that have withstood the test of time.
There is no such thing as writing that will please everyone, just as there is no such thing as a food that everyone likes. But when writing withstands the test of time, when it still sings to most of those who read it long after the writer has died, then it's good or great.