Boxing movies are like movies in general: Some are very, very good –Raging Bull, Rocky, The Set-Up, the original Body and Soul and some are very, very bad – Honeyboy, Goldie and the Boxer and the no-semblance-to-the-1947-classic remake of Body and Soul, starring the clueless Leon Isaac Kennedy in place of the great John Garfield.

The same might be said of boxing documentaries, slices of real life that might not always match the reel-life entertainment value of feature films, but in a way are more compelling because the faces and voices belong to actual persons and not actors.

There have been some praiseworthy documentaries about fights and fighters in recent years. I thought 2007’s Triumph and Tragedy: The Ray Mancini Story  and 2005’s Ring of Fire: The Emile Griffith Story were well-done. But the gold standard for such projects remains 1996’s When We Were Kings, which won an Academy Award as Best Documentary.

When We Were Kings dealt with the mesmerizing “Rumble in the Jungle” between a supposedly past-his-prime Muhammad Ali and the seemingly invincible heavyweight champion, George Foreman, which took place in the early morning hours of Oct. 30, 1974, in Kinshasa, Zaire. Ali, of course, shocked the world – again – and his charisma, cunning and ability to overcome even the most daunting odds were captured on film for the world to cherish and, we should all hope, always remember.

Now comes the counter-point to When We Were Kings, and, to my way of thinking, the second-best boxing documentary ever made. Muhammad and Larry, which premieres on ESPN at 8 p.m. EST next Tuesday, is a cautionary tale that should remind us, if we didn’t already know, that nothing lasts forever, particularly within the harsh confines of the prize ring.

Directed by Albert Maysles and Bradley Kaplan, Muhammad and Larry is the same sad tale we have seen time and again with legendary fighters who believed that the natural laws of diminishing returns did not apply to them, that the force of their will somehow trumped the erosion of their skill. It is easy to imagine a similar documentary about Sugar Ray Leonard’s brutal dual loss to Father Time and Terry Norris, of Joe Louis coming out of retirement for a payday to erase part of his tax debt to the IRS and being knocked unconscious by the young, strong Rocky Marciano. Perhaps some documentarian with vision, like Maysles and Kaplan, will preserve for posterity the final descent down boxing’s slippery slope for the loser of the early-2010 rematch of fortysomething icons Bernard Hopkins and Roy Jones Jr.

But no other fighter before or since could routinely dial up miracles like Ali, who defied the odds so often that he came to believe in his own ability to make magic, like the card tricks he loved to perform before adoring audiences. The world came to believe, too, which is why millions convinced themselves that on Oct. 2, 1980, the old, fat man attempting to whip his body into fighting trim one more time somehow could turn back the calendar and rediscover lost glory.

Ali was so much more than a boxer then, as he is now. Twenty-nine years ago, though, he wasn’t so widely viewed as a tragic figure brought down by the ravaging effects of Parkinson’s Syndrome. He was an idea, an inspiration, a self-made creation who backed up his braggadocio with blinding combinations when he was young and sleek, with determination and heart as he aged and that marvelous physique softened. Regardless of which stage of his career he found himself in at any given moment, Ali never failed to hold the public in his thrall.

After Holmes – a one-time Ali sparring partner who understood the emotional tug his former boss had retained on fans who led with their hearts and not their eyes _ had so battered “The Greatest” that trainer Angelo Dundee would not let his man come out for the 11th round, Jerry Izenberg, the venerable sports columnist for The Star-Ledger in Newark, N.J., sought some answer to why so many had dared to believe their hero again could again make possible what should have been impossible. He got the most telling response from a sextegenarian black wash-room attendant at Caesars Palace in Las Vegas, where the mismatch had taken place.

Izenberg asked the man why he had wagered his hard-earned money on Ali, even when common sense dictated that it was a losing proposition.

“He said, `Because (Ali) gave me my dignity,’” Izenberg recalled. “I never forgot that.”

Izenberg is one of several sports writers who were at ringside that fateful night 29 years ago, all of whom knew what was going to happen but were hoping it wouldn’t be quite as bad as it turned out to be. They reconvened, at the filmmakers’ request, for a sort of round-table discussion of what had gone down and recalled how Ali had taken off so much weight (30 pounds or so), how he was still pretty (he called himself “Dark Gable” because of the mustache he grew during training) and how he could still spout bad poetry as if he were Laurence Olivier reciting a scene from Hamlet.

“He ain’t nothing but a clown with my crown” and “His behind shall be mine in Round 9,” Ali chirped, recalling the days before his Feb. 25, 1964, first meeting with Sonny Liston when he predicted spectators would see “a total eclipse of the Sonny.”

But that Ali, still known as Cassius Clay then, was 21 and this Ali, with extraordinarily high mileage on his boxing odometer, was 37 and a ghost of what he had been. All anyone had to do was to look upon the man dispassionately and without favorable bias, which, of course, was difficult for his legion of true believers.

Ferdie Pacheco, who had recused himself from Ali’s inner circle after the Oct. 1, 1975, “Thrilla in Manila” rubber match with Joe Frazier because he did not want to see him take any more punishment, mused about Ali’s penchant for being roughly handled in sparring at his Deer Lake, Pa., training camp. Ali, who had not fought since his title-reclaiming Sept. 15, 1978, rematch with Leon Spinks, said it was because he needed to “toughen up,” to become reaccustomed to taking hard body shots.

“You don’t toughen up kidneys,” said Pacheco, who served as Ali’s personal physician for 15 years. “Kidneys don’t believe in toughening up because they’re delicate, delicate organs. That’s one of the reasons why (Ali) fell apart” on fight night.

The straight man in this tragi-comedy was Holmes, a good man and an excellent champion whose legacy is forever destined to be overshadowed because his rise coincided with Ali’s fall, and because his star power could never match that which Ali generated with such casual ease.

“For all his life, all he heard was he was a shadow of Ali,” Pacheco said, empathizing with the victor who nonetheless left the arena as something of a victim.

“Holmes deserved to be the next champion after Ali. But he’s not what you would call the successor to Muhammad Ali. He’s just the next guy around. He’s not the next great guy around; he’s just the next guy around.”

There are three reasons why retired fighters return to their brutal trade. They do so because they need another payday, or the adulation that only comes from being active, or because they don’t know how to do anything else.

A profligate spender and generous to a fault with those who pledged their fealty to him, Ali probably was in need of some fast cash. But although he probably still was the most famous individual on the planet, his ego required the sort of constant stroking that only another successful comeback could provide.

With millions of dollars to be made by both fighters, Ali and Holmes agreed to square off because it was financially prudent to do so. Not that Holmes didn’t have second thoughts, however. Like most everyone else, he held Ali in high regard and did not want to see him further damaged.

“I got nothing bad to say about him,” Holmes, an Ali sparring partner from 1971 to ’75, said during the lead-up to the big event. “After I knock him out, he’ll still be my friend.”

Whether Ali was as generous in his assessment of Holmes is a matter of conjecture. An opponent was to be beaten down, even in sparring. Friendship ended the moment someone stood in the other corner.

“He was always good to me,” Holmes said of Ali. “Those things you don’t forget. But I’m going to lay it out. Ali was a great guy. But when it comes down to Ali doing his thing, he wanted to be here (Holmes held his hand up high) and you down there. As long as you’re down there and he’s up here, you’re the greatest thing in the world to him.

“You get in that ring, you got your mother there, your brother there, your sister there, he gonna kick your ass. He ain’t gonna play with you.”

Holmes, no longer anyone’s apprentice, decided he could not play with Ali either. Sure, the “Easton Assassin” knew he was the better fighter then. But what if Ali somehow convinced himself he was impervious to the aging process? Better to go for the quick knockout, Holmes decided, rather than to allow Ali to sway the judges and the audience by hanging around and giving them a reason to believe another miracle was in the making.

Back in Deer Lake, Ali was busy psyching himself into the belief that it somehow was 10 or 15 years earlier and he again was the absolute master of his domain. Could he reach into his trick bag and pull out another rabbit? Become heavyweight champion of the world for an unprecedented fourth time? Well, why not? He was still Muhammad Ali, wasn’t he?

“He can’t move his head,” Ali told a group of sycophants as he watched a tape of the classic June 9, 1978, fight between Holmes and Ken Norton. “He don’t duck, he don’t weave, he don’t crouch. He’s a stand-up-straight fighter. I’ll have no trouble with him. I’ll eat him up.”

Perhaps Ali should have watched more updated tapes of himself instead. “Dark Gable” was shuffling, all right, but not as a part of any preconceived strategy. The master of the Ali Shuffle was about to enter the extreme danger zone.

“Is there any question as to why he fell apart?” asked Pacheco. “Not if you were around looking at him. Not if you saw him every day talking slower, walking slower, moving slower, punching less. You could see him falling apart.”

True to his word, Holmes attempted to take Ali out quickly, to spare him an ongoing bludgeoning. But the Ali who withstood all those trials by fire from Joe Frazier and Foreman refused to yield, so round after round Holmes looked imploringly to referee Richard Green, begging him with his eyes to stop the madness. Except that Green also remembered the Ali who could come back from the brink, and maybe believed there was enough time for him to do so again.

It was left to trainer Angelo Dundee, who remained with Ali well past his expiration point as a great fighter, to step in, as Frazier’s trainer, Eddie Futch, did before the 15th round of the “Thrilla in Manila.” He told Green it was his call as chief second to end it, and he was making that call.

Victory was bittersweet for Holmes, who believes to this day he could have beaten Ali prime-on-prime. But public perception is a fickle thing, and there is no way his thrashing of a legend enabled him to take for himself a measure of that legend’s incredible popularity.

“A lady came up to me in Las Vegas and said, `I hate you,’” Holmes said. “I said `Why?’ And she said, `Because you beat up Muhammad Ali.’”

The ghost of Ali faded further still until the night of Dec. 11, 1981, when he lost a unanimous, 10-round decision to Trevor Berbick in the Bahamas. Three years after that he was diagnosed with Parkinson’s Syndrome.

Might Ali have avoided Parkinson’s had he retired after his conquest of Foreman? After the epic third battle with Frazier? Was there still time to save him from himself had he not been enticed to sign for the inevitable beatdown by Holmes?

So many questions, so few answers. All that remains is the memory of a man who boasted that he was “The Greatest” and, for a large chunk of his boxing life, was just that.