If I look at the chart placement of something like Innervisions
Number 4 in the United States
Number 8 in the UK
Number 26 in Australia
Songs at the key of life was more successful in Australia which came number 6 (while UK no. 2 and USA No. 1)
However in terms of charts of the entire year. it was the 2nd biggest selling album in the USA that year, 18th biggest selling album of the year in the UK and 49th biggest selling album of the year in Australia.
Sure he had popularity here and people would have heard of him but I'm just not that entirely convince of ultra-legendary status
Regarding Prince vs Michael Jackson. When Prince died, the only people on Facebook commenting about his death were the people I became friends with via Babble and Only Solitaire. At work no one was talking about it until I was the person bringing it up which led to some brief conversation about, that people recognised him as the pop star with the weird symbol and probably knew a few hits.
Michael Jackson on the other hand had numerous random people on Facebook commenting when he passed away.