The last time I checked they don't have the same program to immigrate to Australia as they do for Canada. They used to but I think their new government with the conservative leader shut down that program. Again, do not quote me on that as the last time I checked was long time ago and I didn't check it super carefully.
To me? The USA. No question. The major problem is, of course, that there is no good immigration process. Getting F1 is not an issue. Getting H1 with the current demand is borderline impossible. Plus, my spouse won't be able to work until we both get Green Cards. However, if we forget about those problems, then for me, the USA is the best country to immigrate to.
The second option would be Spain. I am in love with that country. Also, sharing the second place with Spain is Canada.
The third option is Netherlands. Then, Germany. Then, Czech Republic.
I have never been to UK but based on what I heard about it from my friends and my cousin, UK is like Canada with lower salaries and better public transportation.