/lit/ - Literature

Good writing is a complicated topic.
Do you mean something that is written nicely? Meaning good prose?
Good prose has to do with expressing what you want to express in a consise, or aesthetic, or overly verbose, or all three and more, manner. Alot of times writing that is "too prosey" can be considered purple, but usually that's more of a personal preference. Good prose, as a baseline, requires variety and style. Having a paragraph filled with sentances that are the same legnth is generally bad because it's boring (but it can work under specific circumstances like pov narration). Good writing will typically mix different legnths of sentances and use a variety of sentance structures (meaning changing the placements of subjects and objects) and will (this is often a sign of great prose) occasionally bend or break the rules of grammer in order to achieve a more aesthetic, pleasing, or stylistically cool effect that evokes emotion. Good prose will also use a strong lexicon and know when to use big, high sounding words, and when to calm down with something base and simple. Good prose will generally avoid using the same word repeatedly unless it is clearly intentional and used with purpose to get some kind of point across. If it ever feels like the author simply "forgot" that he already used that word just one paragraph ago, then it's not good.
But good prose is not everything
Good writing also involves characters. And characters need goals, growth, struggle, change, etc. In order for those thing to happen, you need plot, and plot needs to be believable in its own context, intresting, dynamic, etc. And for the character and plot to work well together, there needs to be a theme that binds them. A reason for reading the words on the page beyond the words on the page. All of this needs to flow back into the prose and work together to create something GOOD.
So yeah. There isnt a simple answer to your question.
Here is one example of something that is, from what I've seen, widely considered to be among some of the best passages ever written