I just came across this website.
OlympicNationalRankings
It says that the top 5 countries were
1. Australia
2. France
3. Great Britain
4. Netherlands
5. USA
It uses probability rankings to determine which country performed the best at the Olympics. It is based on a mathematical formula that appears to be quite complicated.
It takes a 24 page article to explain it. I just went to the results!
It does this by ranking according to the Probability Index U, which has a simple meaning: U measures the improbability that a country of a given population would win as many medals as it has, or more medals, if all people in competitive countries worldwide had equal medal-winning capabilities.