St. George is the only human to be depicted on a national flag (Malta), he is also present on the coat of arms of Moscow and Russia, patron saint of England, and has whole country named in his honour (Georgia). Wikipedia article states he's also 'respected' in Islamic world. So what exactly makes St. George so exceptional?
hi! There's room for more on St George and pre-Christian origins of dragon tales, but you can get started on these earlier posts
As already mentioned in some of the posts linked by /u/Searocksandtrees , a dragon was often seen as the embodiment of Satan. Even in 18th century sources, many disasters are told to been foretold or even caused by a dragon. This wasn't just some mythological creature, it was part of how many medieval christians viewed the world around them. Nature wasn't just a biological reality, it was a plain of spirituality and religion. There were often three 'levels' of life :
So when Saint George fights and defeats a dragon, it's basically a shining example for how divine inspired humanity can defeat Satan and all that is evil. When you consider the fact that many wars were also fought by those who saw themselves as the defenders of faith against he "evil" of others, it makes all the more sense that Saint George was so popular. In a worldview where so much was out of your control because it was either a punishment by God or influenced by Satan, it must have been very tempting and liberating to promote yourself as the champion of God (Saint George) and brand your enemies as "evil" in order to take control of your own faith. It also helped that the origin story of Saint George wasn't very specific. It was about symbolism and inspiring people, so it was easily adapted and appropriated by various groups.