This is my personal points of views:
1. Exactly how many Chinese langauges are there ? Are they to be considered all "dialects" of one great Chinese language ?
2. Or are they simply independent languages of a common origin like French, German, Russian, and Greek ? How far back does the split go back in time ?
3. What are some good sources to ready up on the Chinese languages (whether dialectal or independent) ?
4. Why aren't Mandarin and Cantonese mentioned as the two major "dialects" of Chinese; and from which to explain all the other "dialects" ?
My answer:
Chinese languages and chinese dialects are totally different. Languages of China region (including HK, Macao and Taiwan) are various because China has 56 races, e.g.
Han, Mongols, Tibetan, Korean etc etc... Han speaking Han Chinese 汉语, Mongols use Mongolian, Tibetan using Tibetan, people in Xinjiang talking in Turks or Arabic. In this case, Chinese languages including Mandarin, Mongolian, Tibetan, Arabic..... Yes, eventhough some of those languages maybe is other country's national languages.
In Han Chinese Language, there are various of dialects, such as Mandarin (Official or Beijing), Shanghainese (Shanghai), Hakka (Southern China), Taiwanese/Min (Fujian and Taiwan), Cantonese (Guangdong and HK), Hainanese (Hainan).... There are all considered dialects of Han Chinese. Those dialects have identical language system which mean there all using same Chinese Character but pronouns that specific character in similar or different way.... Like Cantonese and Mandarin, one ˆê is called "Yi" in Mandarin but in Cantonese is "Yak" Nowsaday, lots of chinese dialects is losing their significance, except official Mandarin, only Cantonese (HK) and Min (Taiwan) still playing important in certain regions. However, Chinese language is normally refered to Mandarin Chinese.