iphone not fully 3G capable and IIRC no itunes store in the country.
windows brand new to them but works on 3G
android works on 3G, sideloadable apps, much cheaper smartish phones fromlocal companies.
The winner will be Android, second place will be either of the other 2, ut Apple if they upgrade their phone to work on 3G in China.
Lets be honest here, even the most rabid anti Apple person would be hard pressed to be positive about Windows Phone as an alternative to Android if all things were equal.