Nicest People.
There are all sorts of people in all sorts of places, but the following countries are well-known for the kindness and hospitality of their population.
Iran, Pakistan (Northern areas) and Bangladesh
Ghana, Zimbabwe, Dominica & Sudan
India/Nepal (in the right places/circumstances)
Georgia & Turkey
Honorary mentions.
Cuba and Ethiopia.
As a general rule of thumb, the more travelers the less friendly people get. So head off the beaten track and venture to destinations most would be put off visiting. There are many such suggestions above.