Mayweather-Pacquiao will become richest fight, but how about most historically significant?

By the time Floyd Mayweather and Manny Pacquiao slip between the ropes at the MGM Grand Garden to face each other somewhere around 9:15 p.m. PT on May 2, it will have been nearly 1,900 days since many boxing fans believe they first should have met.

Talks in late 2009 that were aimed at putting the two men into the ring against each other on March 13, 2010, hit a snag when Pacquiao and promoter Bob Arum declined Mayweather's demand for drug testing run by the United States Anti-Doping Agency.

For the better part of the past five years, Question No. 1 in boxing has always been the same: Do you think Floyd and Manny will ever fight?

Now that they are, many are calling it the biggest fight of all time. If it is judged purely in financial terms, nothing else comes close.

Mayweather is expected to receive at least $120 million to fight his rival, while the Filipino superstar figures to make at least $80 million.

Muhammad Ali and Joe Frazier split $5 million for their famous March 8, 1971, bout at New York's Madison Square Garden. Each man's $2.5 million purse, adjusted for inflation, would be $14.6 million in 2014 dollars, according to the Department of Labor's Bureau of Labor Statistic's inflation calculator.

Mike Tyson and Evander Holyfield each earned $30 million for their June 28, 1997, rematch at the MGM Grand in Las Vegas for the heavyweight title. Adjusted for inflation, that would be $44.25 million for each man.

It's a nice purse, indeed, but even combined in 2014 dollars, it's still $31.5 million less than what Mayweather himself will make. Mayweather's purse will be more than many Major League Baseball teams' entire 2015 season payroll. The Pittsburgh Pirates, who have made the playoffs in each of the last two seasons, will begin the year with a projected franchise-record $90 million 40-man roster payroll.

Those kind of dollar figures point out how big the fight is in terms of finances. Nothing in the history of boxing can touch it. But there are a number of fights that easily surpass it in terms of historic significance and that at least equal it in terms of in-ring significance.

Though Mayweather is almost universally regarded as the No. 1 pound-for-pound fighter in the world, the widely held perception is that he has slipped since 2010. He's been hit more than he ever has been in his last two fights, when Marcos Maidana's pressure got to him somewhat. Even as far back as his 2012 match with Miguel Cotto, he walked out of the ring with an uncommon amount of welts, swelling and bruising.

Most experts still consider Pacquiao No. 2 pound-for-pound to Mayweather, though he's lost two times since 2010, including a brutal one-punch knockout at the hands of Juan Manuel Marquez in 2012.

Though at the time it was feared that Pacquiao's knockout loss diminished all hope of a bout with Mayweather, history should have proven that wouldn’t necessarily be the case.

On June 19, 1936, rising American star Joe Louis met former heavyweight champion Max Schmeling of Germany at soldout Yankee Stadium. Louis was favored, but Schmeling totally out-boxed him and stopped him in the 12th round. After the fight, Schmeling received a congratulatory message from German Chancellor Adolf Hitler.

Louis rebounded to win the heavyweight title by knocking out "The Cinderella Man," James J. Braddock, on June 22, 1937, at Comiskey Park in Chicago. After three successful title defenses, as world tensions were rising and World War II was edging ever closer, Louis signed for a rematch with Schmeling for the title on June 22, 1938, at Yankee Stadium.

According to David Margolick's brilliant 2005 book, "Beyond Glory: Joe Louis vs. Max Schmeling, and a World on the Brink," 60 million Americans and 20 million Germans listened to the fight on radio, even though the fight was occurring at 3 a.m. in Germany.

In the introduction to his book, Margolick quoted the New York Mirror's preview story on the fight in an attempt to put it in its historical significance.

"Wars, involving the fate of nations, rage elsewhere on this globe, but the eyes of the world will be focused tonight on a two-man battle in a ribbon of light stabbing the darkness of the Yankee Stadium," the Mirror wrote.

Margolick wrote that there were estimates at the time that there were more journalists covering Louis-Schmeling II at Yankee Stadium than there had been for the signing of the Treaty of Versailles on June 28, 1919, which ended World War I.

The Nazi propaganda machine was also out in a big way for the Louis-Schmeling rematch. After Schmeling's 1936 win, Hitler had a highlight film made called "Schmeling's Victory: A German Victory." A German publication known as "Der Angriff", which was regarded as the mouthpiece of Nazi propaganda minister Joseph Goebbels, wrote "On this day, two men will hold an entire world in the utmost tension."

As big as the Mayweather-Pacquiao fight will be, it doesn't have the kind of social and historical significance of Louis-Schmeling II, which Louis won by first-round knockout.

Most boxing historians regard Ali-Frazier I as the "biggest" bout in the sport's history. That fight pitted two unbeaten men with legitimate claims to the heavyweight title.

Ali, the 1960 Olympic light heavyweight gold medalist, was 31-0, 29 years old and had been stripped of the title for refusing induction into the military service. Frazier, the 1964 Olympic heavyweight gold medalist, won the title after Ali was stripped. He entered the bout with a 26-0 record and 23 knockouts.

Ali, even before the first Frazier bout, was one of the world's most iconic figures, known far beyond simply his sport.

Former Yahoo Sports columnist Michael Arkush wrote "The Fight of the Century," which chronicled Ali-Frazier I. In it, he quoted ex-HBO Sports boxing analyst Larry Merchant about the atmosphere at Madison Square Garden when the bell rang to start the fight:

"There was this guttural roar," Merchant was quoted in Arkush's book. "I can still summon it in my mind's ear. It came straight up from the stomach, from a place that went beyond the heart, that the heart could not control, much less the mind. People could hardly believe the fight was going to happen."

Frazier won by 15-round unamimous decision.

There are several other bouts in history that have had the kind of sporting significance that Mayweather-Pacquiao brings, but the other match that had the kind of societal implications that Louis-Schmeling II did was the 1910 so-called "Great White Hope" bout between champion Jack Jackson and former champion James J. Jeffries.

Johnson in 1903 won what was known then as the "World Colored Heavyweight Championship," given that African-Americans at the time were not permitted to fight for the world title.

Joe Gans became the first African-American to win a world title of any kind when he won the lightweight title in 1902, but African-Americans were prohibited from fighting for the world heavyweight title until Johnson won it on Dec. 26, 1908.

After beating Tommy Burns to win the title in 1908, Johnson fought to a controversial draw with "Philadelphia" Jack O'Brien in 1909, then defeated Tony Ross, Al Kaufman and the great former middleweight champ Stanley Ketchel later that year.

White Americans pleaded for someone to come forward to defeat Johnson and reclaim the belt, and after some coaxing, Jefferies came out of retirement to face him.

Promoter Tex Rickard offered President William H. Taft the job as the fight's referee, which the president politely declined. After Sherlock Holmes creator Arthur Conan Doyle also declined the offer, Rickard himself refereed the fight.

Johnson dominated the July 4, 1910, bout in Reno, Nev., and stopped Jeffries in the 15th round of a scheduled 45-rounder.

Riots around the country began after Johnson's win, and 20 people died and hundreds were injured.

The Mayweather-Pacquiao fight is bound to engender tremendous passion, but it's never going to rise to the level of Louis-Schmeling II or Johnson-Jeffries in terms of societal significance. It will be a megafight in its own way, and deserves respect for that.

It is correct to call it the richest fight in history, but certainly not the biggest.