The modern Summer Olympics started in 1896, providing ample history to draw from to compile a top-10 list of greatest rivalries.
The following list focuses on both individual and team rivalries that I think comprise a representative selection for this discussion:
Michael Phelps vs. Ryan Lochte, 2004-2012: Phelps is the greatest competitive swimmer in history, and he defeated Lochte in three Olympic individual medley races between 2004-2008. However, Lochte finally took a race from Phelps in London by winning the 400-meter event.
U.S. Men's basketball vs. Soviet Union, 1972: The U.S. dominated men's basketball at the Olympics between 1936-1968, winning every title. But the Soviet Union was generally competitive from its first appearance in 1952. In 1972, the Soviets shocked the Americans to win the gold in Munich, taking a game marred by controversy by a score of 51-50.
Shirley Babashoff vs. East German swimmers, 1976: At the Montreal Olympics, Babashoff finished in second place in her three individual events: the 200-meter freestyle, the 400 free, and the 800 free. And each time, she was defeated by an East German swimmer.
Babashoff was criticized by the media for suggesting the East Germans were not better swimmers, but better cheaters by using drugs. Her claims were proven true years later, when it was revealed that they had done so.
U.S. Women's softball vs. Japan, 1996-2008: Although women's softball is no longer a part of the Olympics, the U.S. and Japan went head to head in some memorable matchups, with the U.S. capturing the first three golds. Japan finally got its Olympic title in the sport by upsetting the heavily favored Americans in 2008.
Alexander Popov vs. Gary Hall Jr., 1996: Popov was the best freestyle sprint swimmer for the Soviet Union/Russia in the 1990s, while brash American Gary Hall Jr. arrived in Atlanta looking to make a name for himself. Popov, though, won both the 50-meter and 100-meter freestyles, relegating Hall to the silver each time.
Anton Geesink vs. Akio Kaminaga, 1964: Judo was introduced at the 1964 Olympics. The Japanese were keen to show the rest of the world their greatness in the martial art they created. Their judoka emerged victorious in the first three weight classes, setting the stage for the last gold-medal match between Japan's Kaminaga and Geesink, a giant Dutchman. Geesink promptly dashed Japanese hopes of perfection by pinning Kaminaga to the tatami for the title.
Joan Benoit vs. Grete Waitz, 1984: Benoit took the inaugural Olympic women's marathon for the U.S. in Los Angeles, while Norway's Waitz earned the silver. Both women had great accomplishments in distance running in the years preceding those Games, and their super-fast times in 1984 demonstrated unequivocally how well women could run the marathon.
Kim Jae-Bum vs. Ole Bischof, 2008-2012: South Korea's Kim and Bischof of Germany met in the last two Olympic judo finals at 81 kilograms. Bischof took the title in 2008, with Kim avenging his loss in Beijing by capturing the gold in London.
Kosuke Kitajima vs. Brendan Hansen, 2004-2012: Japan's Kitajima and Brendan Hansen of the U.S. were the world's best men's breaststroke swimmers for nearly all of the past decade, alternating wins at World Championships and the world records in the 100-meter and 200-meter breaststrokes.
However, at the Olympics in 2004 and '08, Kitajima won all four breaststroke medals awarded, while Hansen got just a silver and a bronze in '04. But Hansen got some revenge in London by taking the 100-meter breaststroke bronze, while Kitajima failed to medal.
Leisel Jones vs. Rebecca Soni, 2008: Jones was Australia's great breaststroke swimmer last decade, winning medals in five of six Olympic women's breaststroke events contested between 2000-2008. At the Beijing Games, she swam for gold twice against up-and-coming American Rebecca Soni. Jones won the 100 meters, but Soni captured the gold in the 200 meters and did so in world-record time.
Patrick Hattman covers the Olympics for Yahoo! Contributor Network and looks forward to more drama and excitement from the London Games.