Muriel de France has the answer for you.
I'd just add a couple of things.
QQ International is good, better than QQ for foreigners, but still really difficult. It is a thin layer of English over the Chinese website. Anything strange & you get Chinese messages. QQZONE, emails, &c. are just Chinese.
That said there is a growing number of non-Chinese using it & chatting in QQ groups. This number is small compared to ICQ, MSN, Yahoo & such, but growing.
I guess Muriel de France reads Chinese well. Even while motivated to use it, I gave up trying to use QQ (non-international) as I could not read well enough to register easily nor use it.
Yes, I suspect most use MSN, but I do not know the figures.
For me, QQ (most), --------(long gap)---- ICQ, MSN, ----- Gtalk,----Yahoo (Tried it briefly).
ICQ 100,000,000 accounts
Maybe someone can find the numbers for the others
For me Jabber is better for the others. It connects you to others with one piece of software. I used jabber software called PSI or Exodus.
I suspect many have skype: Some claim better sound. I have used it, but not so much.