Second-tier nations threaten to crash the big two's party
A slew of countries could provide a shock to China and the US and ultimately decide the fate of the two superpowers by snatching precious golds.
Chief among those is Russia.
The days of its Soviet-era dominance are over and in Athens the team were leapfrogged by China to end in third place on the gold count. But does the ranking drop signal a permanent change in the pecking order as the Chinese chase the summit?
Though it would be a hard task to surpass the US, confidence is high in the Russian camp that they can regain second place.
Their Athens third place came courtesy of a 92-medal haul - 27 gold, 27 silver and 38 bronze.
With strong athletes in various disciplines from track and field to ball games, the Russians could claim enough medals to keep the US and China looking over their shoulders.
Despite a small population of 21 million, mighty Australia has come fourth in the past two Games, winning 49 medals in Athens.
With the help of Libby Trickett and Leisel Jones in the pool, the country is aiming for another top-four placing - although Australian Olympic Commission president John Coates recently predicted Australia could be bumped down to fifth by Germany.
Buoyed by topping the medal table at the 2006 Turin Winter Olympics, the Germans - who also won 49 medals, but fewer golds than Australia, in coming sixth in Athens - will be looking for a large medal haul this time. And much of it could come in Hong Kong, thanks to their powerful equestrian team. Germany should also find more riches in the pool, as well as in handball, canoeing/kayaking and rowing.
Great Britain came 10th in Athens, with nine golds and a total medal haul of 30, but the nation expects much more from its athletes, who will carry the Olympic flag back home on August 24. Recent form suggests Team GB could enjoy its best showing at a non-boycotted games since 1920, and leapfrog France, Germany, Italy - and even Australia - up the table, thanks to strong entries in cycling, sailing and track and field.
France finished seventh in Athens with 33 medals, and will again turn to multiple medal-winning pool hero Laure Manaudou for another bumper haul to help improve the nation's medal standing. Fellow swimmer Alain Bernard will be seeking to consolidate his recent blistering pace. Other medal-productive areas should be judo, cycling, sailing and fencing.
Japanese athletes manufactured a huge amount of pride for the country by coming fifth in Athens with the country's largest medal haul ever - 37. The triumph, which included 16 golds, gave hopes of a return to the days of regular top-10 finishes, which Japan has not enjoyed since the early 1980s.
But the reality may prove different, as poor form over the past four years means beating South Korea to the title of Asia's second-best nation behind the hosts is probably Japan's best hope.