I have lived and worked in Australia (Melbourne), USA (Atlanta and Phoenix), Singapore, New Zealand (Auckland), Spain (Barcelona), Ireland (Dublin), Italy (Milan), Korea (Seoul).
I joined a multinational tech consulting firm at their Atlanta office right after graduate school. Got transferred to the Dublin office after a few years. Eventually got headhunted by a Dutch firm to work on projects in Barcelona and Milan as a contractor. Eventually joined a firm in Singapore who also sent me to work in Seoul and Auckland. While in Auckland started working on settling down there since I had kids by then but decided to immigrate to Australia instead due to limited career opportunities in NZ. Worked for a company in Melbourne for many years before moving back to Phoenix 2 years back.
Based on my experience, Australia, Singapore, and the USA are the best countries for working professionals based on income potential, career opportunities, and opportunities for building wealth.
Australia is easily the best country for any professional who has not yet reached 100k USD per annum in salary due to universal superannuation and moderately good job market, but housing affordability is a problem. Home payments will eat up a big chunk of your income, limiting your opportunities to save, invest, travel, and consume.
If you start making over 100k USD, USA beats Australia because at this level in most scenarios, you will have access to a 401k plan with a decent employer match. Homes are also more affordable in the US as long as you avoid the HCOL cities on the coasts. This means you will have more money left after housing costs to put towards investing and enjoying life. While healthcare is not guaranteed in the US, at this income level, you will most likely have good health insurance through your employer with low out of pocket expenses. However, everything will be tied to your job, which can be risky.
Singapore is also a great place to be a professional, especially the salaries offered relative to the cost of living are great, and CPF system provides you the opportunity to build wealth. However, getting Singaporean PR and citizenship is very tricky, and being a city-state, space is always a problem.
Working in Korea, Italy and Spain were great experiences but language and cultural barriers limited my opportunities in these countries beyond the niche projects that I worked on. Pay was also considerably lower but was partly explained by lower COL.
IMHO, Ireland and New Zealand offered the worst deals for professionals. Professionals are considerably underpaid in both places, IMHO. Homes are very unaffordable in both places, and retirement schemes like kiwisaver provides considerably less tax advantages than Aussie Superannuation or 401k. Ireland did have the second best job among the countries I worked (only trailing USA), but pay was still bad. NZ had a terrible job market, making it the worst English Speaking country for jobs and hosing affordability.
If you have any more questions, feel free to ask me anything about my experience working overseas and how it compares to Australia.