Muhammad Ali and Joe Frazier fought three times, including two of the most famous matches ever. Frazier defended his heavyweight championship with a unanimous decision over Ali in 1971 at Madison Square Garden in the "Fight of the Century." Ali won the rematch by decision in 1974. Then came the "Thrilla in Manila" in 1975. Ali won on a TKO after 14 rounds. Honourable mentions: Sugar Ray Leonard vs. Roberto Duran, Ray Robinson vs. Jake LaMotta.
Wilt Chamberlain and Bill Russell went head-to-head 142 times over a decade from 1959-1969. Russell's Boston Celtics beat Chamberlain's teams 85 games. Chamberlain shattered records. Russell collected championship banners, winning nine to Chamberlain's one. Honorable mention: Larry Bird vs. Magic Johnson.
Jack Nicklaus and Arnold Palmer turned golf into a popular spectator sport on television. Nicklaus holds the record with 18 majors while Palmer captured seven in his career. They finished 1-2 four times in majors. Honourable mention: Tiger Woods vs. Phil Mickelson.
Roger Federer has a 17-14 edge over Rafael Nadal in career Grand Slam victories, but the head-to-head rivalry is one-sided. Nadal leads the series 23-11, including a 9-2 record in grand slams. Nadal's victory in the 2008 Wimbledon final is considered one of the best tennis matches in history. Both men also have long rivalries with Novak Djokovic. Honourable mentions: Chris Evert vs. Martina Navratilova; John McEnroe vs. Bjorn Borg.
The two best soccer players in the world play in the same league for two powerhouse teams. Since the Ballon d'Or was first awarded to the world's top player in 2010, Lionel Messi and Cristiano Ronaldo are the only men to win it (Messi, 2010-12, 2015; Ronaldo 2013-14). In 2008, Ronaldo won the FIFA player-of-the-year award, and Messi won in 2009. Messi's Barcelona team won the UEFA championship last season, and Ronaldo's Real Madrid has not won the Spanish league since 2012. Internationally, Messi and Argentina lost to Germany in the finals of the World Cup, while Portugal and Ronaldo failed to get out of the group stage.
The Great One vs. The Magnificent One. Wayne Gretzky and Mario Lemieux dominated the NHL for two decades with one of the two players winning the scoring title every year between 1980 and 1997 except for one season. They never faced each other in the playoffs, however. Honourable mention: Sidney Crosby vs. Alex Ovechkin.
Joltin' Joe vs. The Splendid Splinter. Yankees-Red Sox had to make the baseball list. Ted Williams remains the last player to hit over .400, but his tremendous 1941 season was overshadowed by Joe DiMaggio's 56-game hitting streak. Williams won two AL MVP awards and two triple crowns, but no World Series titles. DiMaggio was a three-time MVP who won nine World Series championships with New York. Honorable mention: Willie Mays vs. Mickey Mantle.