Sports arguments. They're the topic of a million bar bets and the fodder for just as many afternoon drive-time radio shows.

LeBron or Jordan. Brady or Manning. Gretzky or Orr. And so on.

Turns out boxing is no different.

The internet is chock full of lists espousing their authors as a definitive source for both modern and historic pound-for-pound collections. 

Some are worth their weight in clicks, while others are best passed by.

To celebrate a Manny Pacquiao’s Saturday swan song, your favorite Tuesday space-filler joined the fray by compiling a list of the 10 best boxers this century. 

Pacquiao’s rivalry with Floyd Mayweather Jr. spawned arguments on its own before it was consummated with a 2015 fight that the latter won by unanimous nod at the MGM Grand in Las Vegas.

The 10 fighters are presented in alphabetical order.

Canelo Alvarez: The cinnamon-haired Mexican debuted in 2005, was a champion by 2011 and has spent the last 10 years collecting hardware at every division from 154 to 175, with no discernable signs of a slowdown.

In fact, given his preeminence, the biggest questions around him these days aren't about how good he is, but whether there are many legitimate worlds left for him to conquer.

Joe Calzaghe: He became a standout in the United Kingdom after beating Chris Eubank for the lightly regarded WBO belt at 168 pounds in 1997, but he didn't get over in the United States until nine years and 17 defenses later when he competitively undressed then-unbeaten IBF claimant Jeff Lacy before a rabid crowd in Manchester.

He fought three more times at super middleweight before jumping the Atlantic to land big-name 175-pound fish in the final two bouts of his career across seven months in 2008, rising from first-round knockdowns to defeat Bernard Hopkins in Las Vegas and Roy Jones Jr. in a Madison Square Garden finale.

Forty-six fights. Forty-six wins. Need we say more?

Bernard Hopkins: The ornery Philadelphian had recent history's most calendar-defying career in the first two decades of the 21st century, remaining relevant and on a championship level until he was nearly 50 years old.

Though he broke in the century as a young, spry 35-year-old, "The Executioner" worked his way to household-name status as the years wound on, stopping Felix Trinidad in a post-9/11 spectacle at Madison Square Garden in 2001, handling Oscar De La Hoya three years later and reinventing himself as a light heavyweight with a shocking (to some) defeat of then-king Antonio Tarver as a 41-year-old in 2006.

Eight more wins followed against all manner of foes, from unbeaten champs like Kelly Pavlik to shopworn old rivals such as Roy Jones Jr. The title ride finally ended with a convincing 12-round loss to Sergey Kovalev two months before birthday No. 50, and the end of the line was punctuated when Hopkins was knocked from the ring in a KO loss to future champ Joe Smith a month ahead of turning 52.

Not an ideal exit, but nobody of recent stock has done it better older than "B-Hop."

Naoya Inoue: Some guys are here based on what they've done. And others made the list based both on what's occurred, and what seems to remain. File Japanese superstar Naoya Inoue among the latter.

The 28-year-old "Monster" has spent nine years as a pro terrorizing the lighter weight classes—winning a belt at 108 pounds in just his sixth pro fight and climbing the ladder to subsequent titles at 115 and 118.

In fact, each of his 15 bouts since that initial title win has come with gold on the line and Inoue has done his work in violent style, finishing all but two of his opponents. He's logged just 117 rounds across 21 pro fights, an average of just more than 5.5 rounds per outing.

A unification with fellow bantamweight champ John Riel Casimero will only enhance the burgeoning legend.

Roy Jones Jr.: If only Roy Jones Jr. had walked away a little sooner, his "eye test" score on lists like these would be higher.

Say, for example, he'd exited after an improbable rise to heavyweight to unseat then-WBA claimant John Ruiz in 2003 and therefore wound up 48-1 with titles in four weight classes and a first-round rematch KO of the only man (Montell Griffin) to beat him.

Then 2004 happened.

Jones followed Ruiz with a shrink down back to 175 for a majority decision over Antonio Tarver, but was starched by his Floridian rival the following spring and careened through 14 more years of name-recognition mediocrity before finally wrapping with a decision over 11-loss pug Scott Sigmon in 2018.

From 48-1 to 66-9. But the first chapter was too good not to notice.

Wladimir Klitschko: Do you value a long-term body of work—to the tune of 25 wins in 29 title fights across 17 years—or the one-sided result of a single fight in which two judges gave his foe eight rounds and a third gave him nine?

Such is the fodder for the debate between Wladimir Klitschko and Tyson Fury.

The Ukrainian behemoth presented the former argument, earning a pair of title reigns and running roughshod over the division while reaching title defense numbers reserved for the likes of Larry Holmes and Joe Louis.

He was at his best under the tutelage of Emanuel Steward, becoming an offensive juggernaut thanks to a 6'6" frame and pterodactyl-like 81" reach.

Didn't matter against Fury, though, as the Englishman clutched, grabbed and flitted his way to a wide victory that propelled him to a lineal title claim he still holds on the verge of a trilogy fight with Deontay Wilder.

Juan Manuel Marquez: Once upon a time, their names were inseparable. Whenever you mentioned Manny Pacquiao, a Juan Manuel Marquez callout came next.

After all, the two fought four times across three weight classes and eight years, with three fights going to the scorecards while the fourth ended in what still reigns as the century's most dramatic high-profile KO.

Marquez fared pretty well when fighting others, too, gathering titles at 126, 130 and 135 pounds and scoring the stoppage over Pacquiao in a non-title bout at 147 before a final failed belt bid against Tim Bradley.

A fifth bout with the Filipino never materialized, but the resume speaks for itself.

Floyd Mayweather Jr.: Speaking of guys who've beaten Pacquiao, here's another.

Mayweather emerged from the 1996 Olympics with a bronze medal, but it was the last time in his ring career that he'd wound up as anything but an A-side.

He was a second-round KO winner in his first fight, a champion by his 18th and on the verge of a full-scale breakout by the time 2000 arrived. He whipped a previously unbeaten Diego Corrales in his third fight of the new century and didn't stop climbing until he'd won belts in five weight classes.

He became the top draw in pay-per-view history along the way, too, playing the high card in each of the four biggest fights from 2007 to 2017 against Oscar De La Hoya, Canelo Alvarez, Pacquiao and Conor McGregor.

Manny Pacquiao: It's a blueprint unlike any other.

Manny Pacquiao started his career as a teenage junior flyweight and arrived to Las Vegas on Saturday with a chance to regain a belt he won 41 pounds and 24 years later.

In between, he captured sanctioning body titles in seven weight classes from 112 to 154, beat some of the better fighters of the era and cemented his case as a first-ballot Hall of Famer if he ever retires.

Ugas loss or no Ugas loss, the guy was remarkable.

Andre Ward: Ward punched low-profile clocks in Temecula, Portland and the Cayman Islands before reaching the big time with a defeat of then-champ Mikkel Kessler for the WBA's title at 168 pounds.

Six defenses followed as he gradually raised his pound-for-pound profile, including a dominant stoppage of light heavyweight champ Chad Dawson after the bigger man's ill-advised drop from 175.

Injuries and promotional wrangling kept Ward from frequent activity, but he was brilliant every time he climbed through the ropes, ultimately moving to light heavyweight himself for consecutive defeats of Kovalev—including an eighth-round TKO in their rematch, which also turned out to be his last fight in 2017.

* * * * * * * * * *

This week’s title-fight schedule: 

No title fights scheduled.

Last week's picks: 0-1 (Loss: Pacquiao)

2021 picks record: 27-9 (75.0 percent) 

Overall picks record: 1,183-384 (75.4 percent) 

NOTE: Fights previewed are only those involving a sanctioning body's full-fledged title-holder – no interim, diamond, silver, etc. Fights for WBA "world championships" are only included if no "super champion" exists in the weight class. 

Lyle Fitzsimmons has covered professional boxing since 1995 and written a weekly column for Boxing Scene since 2008. He is a full voting member of the Boxing Writers Association of America. Reach him at fitzbitz@msn.com or follow him on Twitter – @fitzbitz.