I would add compare it with energy-related industries private or public. Each of Shell, Exxon, Sinopec and China national petroleum earn 3 times as much as Apple. 6/10 biggest companies by income are in oil/gas, and privately owned companies are a fraction of the industry size...
I wouldn't say private since these are corporations usually based on shares systems. This is different from a company such as Valve, for example, which is purely private and where the revenue information is not publicly available.
Apart from this detail, your point is very interesting. I wonder, all industries considered, how much % of worldwide's revenue is earned by nationally owned companies versus the corporations counterparts.
To what end? Looking at revenue in isolation is mostly pointless. The presented companies have vastly different businesses with different revenue flows.
Shell, by the way, is $14,800/second. These numbers are public and trivially discoverable.
IMO the visual on the page was annoying, and not very informative.
The bar chart somebody linked to showed the same data in a much nicer way. Easier to grasp at a glance, and easier to make comparisons.
To make the page's visual work it would have been better to show later numbers in terms of the previous companies. Show, for example, that Facebook is 1.3 Blackberries, Nokia is 4 Facebooks, etc.