LOL.. comparing China with Japan. The latter has been perhaps the strongest football team from AFC for the last few decades. IMO, they are better than South Korea, Iran, Australia and Saudi Arabia. But the only drawback is now the demographics. Unlike the case with Saudi Arabia or Uzbekistan, Japan doesn't have a very young population. And this means that the player pool is shrinking. That said, despite having such a huge population, what has China achieved so far?
China not significant improvement yet although last four or five season ago many top players play with Chinese Super League team, have been longer time the Chinese club not performed at AFC Champion League but Japan club always dominance. Not important yet about how many population of China but can't have top talent player exactly in football, difference with Japan easily every season their player aboard to top European club.
Interested for upcoming FIFA Club World Cup event have any team from Asian can qualify to higher round or reach to semifinal round, in this time event only Al Hilal can qualify to quarter final.