Joe Frazier had to wait until death to win rightful appreciation after a boxing career spent in the shadow of the magnificent Muhammad Ali, boxing historian Bert Sugar said.

- Ali leads tributes to Joe Frazier

"He never got his due," Sugar said on Tuesday when asked about the former world heavyweight champion, who fought three epic bouts with Ali in the 1970s and died late on Monday from liver cancer at age 67.

"People say Ali-Frazier, and the winner of that fight was Frazier," Sugar said about their first clash in March of 1971, a battle of undefeated heavyweights at Madison Square Garden that left both boxers hospitalised.

"This is the day for Joe Frazier, who has always been the second slot to Muhammad Ali, even when he won. Today is the day when he stands up as his own and he's Joe Frazier, period, paragraph, and he can stand up to anybody on his own."

Boxing promoter Bob Arum said the three bouts between the fighters stood as a hallmark in sport.

"He gave the world what had to be one of the most thrilling trilogies in any sport," he said about Frazier's bouts against Ali. "There was nothing like it in this country and in the world for the attention those fights received."

Ali returned after a three-year exile imposed after he refused induction for the Vietnam War due to his Muslim beliefs to face Frazier and the build-up was intense.

"I think the first, certainly was the biggest event I ever covered. It seemed like the world stopped in anticipation of it," HBO fight commentator Larry Merchant said.

"It was building up for several years, two heavyweight champions. Ali in exile.

"And then to have the fight and the drama exceed the highest expectations, was a once-in-a-half-century, thrilling event."

Merchant did not think Frazier was slighted by his association with Ali, but rather enhanced.

"Regardless of the fact that Ali was such a towering figure in his time, a worldwide figure, he brought out the best in Joe Frazier," said Merchant.

"Indeed Frazier was admired and respected widely and had the heavyweight stage to himself during Ali's exile... in boxing, nobody didn't love Joe Frazier and what he represented in his honesty, dedication and toughness as a champion.

"It was one extraordinary man against an ordinary Joe in terms of personalities and how they reached out to the world."

Pulitzer Prize winning columnist Dave Anderson of the New York Times wrote that he considered Frazier a better fighter.

"I've always believed that, each at his best, Joe Frazier... was the better fighter," Anderson wrote in his column.

Ali won their Garden rematch by decision, setting up the "Thrilla in Manila" rubber bout in 1975. Ali won that rough bout, but Anderson said Frazier inflicted more punishment.

"The Thrilla in Manila in 1975 was awarded to Ali when Frazier's trainer, Eddie Futch, wouldn't let him answer the bell for the 15th round because he couldn't see the right hands coming out of his closed left eye," recalled Anderson.

"But Frazier soon talked freely in the interview area. When an exhausted Ali finally arrived, he described their epic in brutality as 'next to death.'

"That evening, at a party in an old Filipino palace, Ali, his ribs battered, walked stiffly and sat stiffly, painfully offering a finger or two instead of shaking hands. At his hotel, Frazier sang and danced. Seeing them both, if you didn't know what had happened in the fight you had to think Frazier was the winner."

Said Sugar: "Had he stood up off his stool and gone to the center of the ring, Ali would have collapsed. Ali has no legs, they have to almost drag him to the corner after the last round. He would have lost. That's one of the ironies."

Some diminish Frazier in historical terms because his career ebbed after his three epic fights against Ali.

"It is no surprise that after that night of greatness, he was never the same," Wally Matthews wrote for espn.com about Frazier's ferocious victory in their first fight.

"But to knock Frazier for being unable to match the greatest athletic performance ever seen at Madison Square Garden is like criticizing Michelangelo for being unable to sculpt another David."