China's 1.3 billion people make it the most populous country on earth. It is purposefully growing its economy and participating more in the world economy, making its rapid growth a magnet for investors.
Perhaps China is to investors what Barack Obama was to liberals. The name alone causes heartbeats to quicken, and the chance to get involved ... sign me up, sign me up!
China initiated reforms in the late 1970s to move itself away from a government-controlled economy and toward a market economy, dramatically increasing output. The nation has a centuries-old practice of isolating itself from the outside world, so opening its markets to trade was a big deal, both for its citizens living in poverty and for countries looking to buy and sell things.
Keep in mind that China is still a Communist state, so things can change rapidly and arbitrarily, and processes won't be as transparent as investors in the West are used to. China can also be a militarily volatile country.
The recentness of China's start on a market economy tells investors that it has lots of room to run. The industries and the companies within them are just getting started. The American economy is mature and developed. China's is not; it's what they call "emerging."
China's gross domestic product in terms of purchasing power parity was an estimated $7.8 trillion in 2008, according to the CIA World Factbook, with per-capita GDP of $6,100. Industry accounted for nearly half of GDP.