At the moment all time-travel related movies are banned in China (check out the link). I\'m not sure if this still applies, but all ghost related and superstitious themed movies were also banned, hence limiting the scope of the fantasy genre. In general, China has a very weird attitude to science fiction and fantasy because somehow they think it might encourage radical thinking or something bizarre like that....
The simplest answer would be: money. Most Chinese movies don\'t have the budgets to pull off the special effects required for a good sci-fi movie
I believe I have seen some of those sci-fi movies here in China, the last time was a couple years ago though, about a robot, Iron Man style. Forgot the title.