Keesje - Hate to be pedantic but many of those aircraft are actually updated copies (either licence built versions or otherwise) of Soviet-era designs.
A fair bit of tarted up SU-27, AN-12 and TU-16 underpinnings among that lot. Not that its a bad thing of course using such aircraft, especially in the numbers they have, but the Chinese have a fairly well deserved reputation for just copying other people's designs through fair means or foul.