I am fortunate to have already experienced the "Do I belong here?" feeling from graduate school. The thing to remember is this - there are always people who are going to be ahead of you just by virtue of having more experience. How you carry yourself is the most important thing though.

In this context, if you see someone who is better than you at the moment, do some work trying to improve yourself and your abilities. The best don't become the best instantaneously - they do it through hard work & maybe a little talent.

My own experience probably has helped me take on the correct perspective in my own career as a developer - I do things purely because I want to do it or improve myself. I don't care about being the most popular/well-known developer or anything like that - it is a job that I happen to like is all. Stars/likes/etc. on GitHub, those don't matter. I create stuff for fun, and if it becomes popular, so be it - I work on open source stuff in the hopes it helps people and to improve my own abilities.