It depends, each country has something to offer. I really like to go somewhere where you just don’t expect something/you have completely wrong picture about it. Just nice surprise every time you travel there. Also for travel it has to have the “I want to go there” factor, when I say to someone that USA is for me no go country because of this they usually don’t understand.
I would like to travel across the Europe, each country is interesting, even Russia (but visit Russia before Russia visits you and I just don’t want to go there now).
From Asia there are few interesting countries, Taiwan and South Korea.
On Africa I just don’t know, certainly I would like to go to Morocco, but some other countries there are on the list.
Australia and New Zealand are also high on the “I want to go there” index.