Well, the wikipedia articles on human development and developed nations seem to indicate that to be considered a "developed nation" you have to have good per-capita rates, widespread infrastructure (admittedly, while China has first-rate infrastructure, it is only present in urban centers, to hell with rural areas!), and probably the most critical point re China is that you are into a Post-Industrial economy, with a larger service sector than industrial sector.

As far as my readings and knowledge can tell, the above are indeed points where China fails.