I've been wanting to learn Chinese, but I'm not sure Chinese subtitles would help that much compared to if I were learning a European language. Maybe if the subtitles were in pinyin, but I don't know if that would even be an option for a lot of media.
Watching Chinese TV shows with Chinese subtitles definitely helped me a lot, not only because the subtitles gave me a second chance to get what I missed (which is the same with other languages), but also because I could learn characters for those words I could already recognise in speech.
