Thanks for your reply.First of all, I am one of those who is against using the abbreviation 'etc' at all, but especially in a sample sentence like yours. It adds nothing to the sentence and complicates discussing it. Just say ' ... countries like China and Japan' if you can't be bothered to mention any others.
If you do mention others, separate them by a comma but use 'and' between the last and second last.
"Most of all I'd like to visit the countries of the far east: China, Japan, Vietnam and Myanmar."
If we take another example:I think I should put and between the two countries, but not sure of it.