The most important elements of good writing, as per my personal POV, are:
1) It should satisfy your internal hunger for writing.
2) It should be clear and simple enough for most people to understand.
3) It should keep the reader engrossed until the last page.
4) Free from common spelling and common grammatical mistakes.
5) It should be complete, even if it is a series. Don't keep too many ends open to irritate the reader.
6) It should not be filled with unwanted and unnecessary details.
7) Don't wait too long to start the main theme of the story, or your readers will lose interest.