You need to develop your own measure of what good is to you. And as you meet those measures, come up with new ones. In the past I thought I'd be good if I could maintain 30kmh for an hour of city cycling, including stops/starts/lights etc. Once attained I started thinking about a distance measure, thinking that if I could do a metric century in under 3 hours then I'd be good. Now I'm starting to focus on other measures (i.e. watts) and longer weekly/annual distances, higher speeds. No matter how good you think you are, there's always people that are better. You can't let that tarnish your enjoyment of cycling nor deter you in meeting your own definition of "good". In the end we're all good cyclists if we continue cycling to the best of our ability.