Which of these languages...

is the most worth learning, in your opinion, and why?

Russian, Turkish, Urdu, Punjabi, Korean, Hindi, Arabic, Chinese, Bengali.

Additionally, which countries that speak these languages are pleasant and which are shitty?

>>25
That doesn't count for shit look at the mongol empire:
http://www.thelatinlibrary.com/imperialism/maps/mongol.gif

and the control of the Muslim Empires (abbasid)
http://en.wikipedia.org/wiki/Image:Abbasids_Dynasty_750_-_1258_(AD).PNG

Just because they WERE awesome doesn't mean you should learn the language. Look at were they are now.