It's interesting seeing the difference in treatment for people from different countries. As an American citizen, I get to cruise through immigration in most countries, usually without obtaining a visa beforehand. This was the case in Japan, Korea, Indonesia, Philippines when I visited. Most of Europe (Schengen countries) also have this policy. Maybe this colors my perception of those countries in a more positive light.
i've been to half of the countries you listed(england, japan, indonesia and korea) and was pleased by their airport's staff attitude and helpful behaviour.
I agree about Changi and Seoul. Changi is one of the nicest place to transit from. The new airport in Dubai is a mess. It is a very large facility with very low quality, untrained manpower.
Similarly I have determined you can judge an American neighborhood by it's public library.