Great points... and really a discussion we should have more of here...
China is the world's biggest country in population. That's what I assumed we were measuring in the context of this thread but we can certainly look at other metrics, good call.
China has 513 million people online. That's more than the online population of the the #2 internet user, the US (225mm). -USA Today
GDP measures the world on a single scale without accounting for how a local market acts.
In china middle class earn over anywhere from $5,900 - $9,000 US a year depending on the source, the so-called urban elites earn over $12,500.
The US standard for poverty is $22,350.
Projections on the size of the middle class market vary wildly from 100 million to 247 million.
But the same time the concept of costs are relative to the market price.
...it should be noted that disposable income stretches farther in China, on average, than it does in the United States or Europe. A significant portion of household budgets are expended on services, ranging from hair salons to meal at restaurants to travel. Services are usually labor-intensive tasks whose cost is attuned, in part, to the prevailing wage. In China, due to the vast supply of labor, wages are significantly lower than in the West.
Or perhaps from another country's perspective
Compare housing prices in London to Beijing. Although London is not 6 times as high [GPD in the UK is 6x as high], a survey conducted in 2007 showed that London house prices are 12 times the per capita income [of China]; in a good area it could even be 16 times the per capita income!
I remember getting into long discussions with our Chinese marketing director a couple years back. I refused to believe the quotes for service she was getting were accurate or would product the right level of results. I didn't understand the market or customer. I had the privilege of spending months learning about both -- now I know how little I know about it.
As a result China can still drive huge sales.
Over 60% of Nike’s 2010 earnings came from emerging markets, most of it in Asia - forbes
By the end of 2009, more than 80% of the top luxury brands had entered the Chinese market.
On a strict dollar to dollar basis there shouldn't be any knockoff Apple stores in China as at their income level there shouldn't be any need for Apple products but if you've ever done business in China you know that people will literally skip meals to get certain products. The perception of value, luxury, brands all changes dramatically when labor is nearly free.
Clearly China is not #1 in buying "disposable goods".
Asia’s leading independent brokerage and investment group, forecasts demand for luxury goods and travel from Greater Chinese to account for 44% of global sales by 2020, up from 15% today (2011) - CLSA
China is the biggest in size, not in value
The original question was what engines are most used in the top 50 and on the basis of population (my original comment), internet population and soon in middle class population, China is at the top of ladder. In other categories that have significant bearing as well, it is not #1, at least not today.
As for the importance or value of that, well, as you said, if you can't make a profit, who cares.... but what you can profit from is not the same as what I can and vise-verse.
Just as much of China's disposable income goes to local brands I suspect most sites that thrive in China for now will be local for the same dynamic... there's not enough return for someone in the west to make China-level profits unless you simply have Google-size scale.