Are you rich? Almost any country will accept you easily. Are you poor? Forget it just about everywhere.
Assuming you are in between:
1) Does a country with a points based system (e.g. Australia) list your skills as ones they want. 2) What is your home country? Are there countries it is easy to emigrate to (e.g. EU to EU is an entitlement). 3) Do you have ancestors from a country you would like to go to. Many countries (e.g. UK, India*) allow in grand-children of emigrants.
Define quality of life. In a rich country you may have better restaurants and nightlife, on the other hand a poor country may mean you can afford domestics or a much bigger house. Major European capitals are good for culture (museums, art galleries, theatre).
Most important of all: read the rules carefully. Ask a real lawyer if in doubt. Some people have lost an entitlement to British citizenship by getting overseas (i.e. second class) citizenship of India: if they got British first they could had both. I know Sri Lankan who did not know she is (not "entitled to", IS) a British citizen by descent (she was applying for a visa every year to visit her father, she could have got a passport).
This completely depends upon the rules and regulations of different countries. All countries allow nationals of some countries easily whereas for some other nationals they are doubtful. Thus if you want to migrate to some other country do your homework properly.