Learn Mandarin, regardless of what dialect/language you speak in China everyone has to learn Mandarin.

 Yeah, and I wonder who we have to thank for that. Giving up individuality and even religion. :)

From what I've learned in my Japanese course, the symbols of Kanji have the sam meaning as those of Mandarin, however they are pronounced differently.

 Unfortunate but true.  At least it hasn't happened as quickly as was originally planned.  It was initially hoped that all dialects could be phased out and have everyone speaking Mandarin within 50 years, i.e. by 2000 but in reality it's going to take alot longer. Having so many dialects is a huge barrier to development though.

No, Putonghua is not an invention of Zhongguo Gongchandang, it has been in use as the lingua franca for centuries. Individuality and religion, its not like those two have ever existed officially in China :)

Edit: And yes, before you choose, try to spend 3-6 months in each country and see what you think about it.

IMO India feels like the one of the three that it is hardest to adapt to, more misery and explicit poverty most everywhere, people are (I believe) less friendly to foreigners than in China.

I would say Japanese, I am learning it myself atm. Japan is an a amazing country with an awesome language. I myself hope to be there someday. Just be prepared to work extremely hard, and it will cost alot. I haven't been to bed in 3 days so I'm too tired to look up the economy but its pretty good.

Actually most statistics suggest that Mandarin is the most spoken first language, but more people know at least some degree of English. Mandarin is definitely going to get more popular in the rest of the world during the next few decades, but I don't see it ever taking the number one spot in total L1+L2+L3 speakers.

Thanks for your help everyone , i've read every single post and the info has been very usefull.

I think i'm going to pick up where I left off learning french , learn chineese and then eventualy learn japaneese.

I think I'd have more fun with the japaneese language considering I like the culture alot more but from an economic perspective Chineese looks like a more viable language to learn right now.

UPDATE : Does anyone know how I could go about learning CHineese withou actualy going to china ?

Any usefull reosurces ?

No courses at your university? Maybe some other organization holds courses where you live? If not, then I'd try googling.

Japanese has the big advantage that there are a crapload of awesome sites to learn it from, like this, this, and this.. There are probably some for Mandarin too, but I don't know any.