Programming is an open ended non competitive (generally) activity. I don't think there is any meaning in trying to quantify "goodness" and in fact might blind you to possibilities.

So, for myself, the thing I pay attention to is my ease of expressing the things I want to create. I also pay attention to my ability to produce things with certain "qualities" correctness, simplicity, and how modular and composable my code is. There is no objective measure of those things and my understanding of those things constantly expands. I learn these things through by my own experience and looking at what other people are doing and having in depth discussions about programming ( and outside of programming ).

So I have no idea how good I am, but I have confidence in what things I can create and confidence in my ability to learn more.