All the countries bordering China, as indeed China itself, before that mass destroyer, the First Emperor, had many different language origins. Roughly they belong to several major linguistic families. All you have to do is to surf on the internet for 5 mins you will find out much more (type in the search key words : origins korean language).The Chinese languages (note that I state the Chinese languages in plural and I know in modern time there is just one) , as indeed Tibetan and Vietnamese etc. belong to the Sino-Tibetan Family. However the Korean and Japanese languages belong to another major family of languages , the altaic family , which is distinct from the Sino Tibetan family of languages. Of course in the last few thousands years these border nations have adopted much of the Chinese language but they all had different origins and are certainly not originated from the Chinese language as we know in the last few thousand years. The Chinese language evolved to the present form in the same way as indeed the Tibetan and Vietnamese languages. The reason why there is much abundance of Chinese in these bordering countries was due to the flow of business and economic wealth. In exactly the same way why English words cross into the Chinese language today. In Hong Kong where is much more English influence, many Cantonese words now have their origins from English.
Canto is no that important anymore. MOre and more people are learning Mandarin because of the economy in China
Your reference doesn't prove your statement. That Wikipedia statistic is about native speakers. Most of native speakers speaks another language and in most case, it's english. http://www2.ignatius.edu/faculty/turner/languages.htm This study shows that if you add the secondary language to the primary language, the most spoken still is Mandarin, but the second most is English. I'm aware that this study was done almost 10 years ago, but taken that more and more people are learning English, I doubt it would have changed.
You can't say that Canto isn't imoportant. Canto is just as important as Mando to those ppl who use the language everyday. To say Canto isn't important is like saying we all should ditch our native language and get used to English. If you want to settle down in the mainland then, okey it is almost useless to know Canto there, since most of them speak Mando, but yet you can't say one language is more important than another.
mandarin is really important because it will be used for business transactions.. but of course english will be the main language..