''Better life'' I believe is very subjective and depends from person to person. Lot of people right now are in high income bracket & live in very affluent areas where they can get whatever they want. Especially nannies, house help, access to clean water and electricity 24/7, etc. Now for this person, moving to Canada may not exactly translate to better life if he/she chooses to live the same life they had back home. The cost of house help, nannies is a lot when compared to 3rd world countries. Taxes are heavy. Housing is expensive and way more. So even if the person makes exactly same salary in Canada, he would be expected to cut down on a lot of things.
Now for a person who falls in middle class and lower bracket, this will definitely be life changing in terms of overall quality of life, access to better products, services, quality education, decent housing, etc.
Now for me, I have lived abroad in developed countries most of my life but unfortunately most countries don't have a PR program especially for people coming from certain countries so you end up renewing your work permit forever. I wish to move to Canada to eliminate that instability and I really look forward to inculcate the Canadian culture, invest in that country and at some point even look to start my own business. I truly believe if the country is giving me this opportunity, I should give it back as much as I can as well.