PetroChina, the country's biggest oil and gas producer, has overtaken Exxon Mobil to rank first in the latest Financial Times annual list of the world's 500 most valuable listed companies, with a market capitalization of $329.3 billion. This is the first time that a Chinese company has secured the top spot in the 14-year-old ranking. Last year, PetroChina ranked second.

The performance of PetroChina should be a reason to cheer, but suspicions abound about its real competitiveness.

Dong Xiucheng, Deputy Director of the School of Business Administration of the China University of Petroleum, said PetroChina's ranking was due to a slump in market value of U.S. and European companies, which buckled under the weight of the financial crisis.

In addition, the success of PetroChina is more a result of a market monopoly instead of management expertise or technological innovation, said Feng Pengcheng, a senior researcher of the University of International Business and Economics.

There are three Chinese companies in the Financial Times' top 10, with the Industrial and Commercial Bank of China retaining its fourth position and China Mobile falling to No.10 from last year's No.5.

Altogether 45 Chinese companies made the list, and 21 of them are from China's mainland. The Financial Times Global 500, based on listed companies' market capitalization, provides a snapshot of the corporate world.