同一个世界，同一个希望
One World, One Dream was selected, on June 26, 2005 after a judging process involving over 200,000 suggestions, to be the official slogan for the 2008 Summer Olympics.
A world-wide month-long competition, starting on New Year's Day 2005, received the many entries by email or letter. The bulk of the entries were, as might have been expected, from the Chinese mainland, with the majority of these offering suggestions in both English and Chinese.
Losing entries cited in the press release included "Carrying on the Olympic Spirit"†, and "Live in Harmony". According to the director of BOCOG's Culture and Ceremony department, Zhang Ming, a total of ten rounds of deliberation were required (five involving "national experts" and five featuring "international experts"). At the end of this process, however, the committee settled on the self-penned "One World, One Dream."
Commentators have pointed to similar "consensus" decisions coming from previous Beijng Olympics "competitions". A similar "consensus" is expected for the mascot design "competition", expected (as of this writing) to be announced later in 2005. Chinese news reports have stressed that the "unity" "world" and "dream" words/concepts "came up" frequently in the many entries.
UPDATE: The 2008 Olympic Mascots have been announced, and the process was identical, eschewing all 624 actual entries for a "consensus" design.
Early strong contender and genuine entry "Live in Harmony" was eventually discarded because, in the words of commitee member Fan Jingyi, Dean of Tsinghua University School of Journalism and Communication. "...it lacks a modern dynamic and the competitive spirit of sport. What's more, due to the different cultural backgrounds of people throughout the world, it is less powerful in Western cultures than it is in China. Therefore we dropped the word from our final list." Having heard Fan, former editor-in-chief at People's Daily, speak in Beijing on the topic of Western culture, I can attest to this being very much the style of wildly mischaracterizing generalisation that he seems to favour.
An argument could be made that a more accurate translation of the Chinese might be "(We're of the) Same World, (We've got the) Same Dream", "One World Together, The Same Dream" or even "The World Agrees On The Same Dream" - but the official translation certainly rolls off the tongue and captures the essence of the less pedantic side of the Chinese version, which assumes agreement with the sentiment just a tiny bit too much. It might, as it usually is in these cases, be more accurate to say that there are two slogans, an English and a Chinese one that are similar in meaning.
References:
http://www.chinadaily.com.cn/
http://www.chinadaily.com.cn/english/doc/2005-06/27/content_454886.htm
http://www.bbc.co.uk
† Yikes! Isn't this one redolent with double meaning?! Chinglish is everywhere...