LONDON — The greatest?

When it comes to Michael Phelps, the answer seems obvious with just a cursory glance of the medals table.

The guy has won 15 golds — “insane,” says Serena Williams, who certainly knows a thing or two about winning — and now he’s got more total Olympic medals than anyone, with a few more races to extend the record into almost unfathomable territory before he’s done in London.

Even President Barack Obama jumped on the bandwagon, phoning Phelps on Wednesday to congratulate him on his remarkable accomplishment.

“He’s definitely the greatest Olympian of all time,” said South African swimmer Chad le Clos, who’s actually one of the few guys to have beaten Phelps at the Olympics. “He’s my idol.”

But the greatest?

That’s where things get a bit dicier.

While the sporting world — everyone from Masters champion Bubba Watson to Spanish soccer star Gerard Pique — peppered Phelps with praise in the Twitter-verse after he earned the 19th medal of his career, no less an authority than Sebastian Coe was reticent to bestow the ultimate crown.

“My personal view is I’m not sure he’s the greatest,” Lord Coe said Wednesday, speaking as a two-time gold medalist in athletics and the face of these games as head of the London organizing committee. “But he’s certainly the most successful.”

Others think the sheer magnitude of Phelps’ accomplishments leave little doubt about his place in history.

“He’s won more medals that any Olympian in history,” said U.S. swimmer Tyler Clary. “That should speak for itself.”

Indeed, the numbers are mind-boggling:

• Start with the golds. Phelps has six more than anyone else. If he wins his last three events in London, he’ll have twice as many as anyone else.

• Soviet-era gymnast Larisa Latynina previously held the record for total medals, winning 18 over a span of three Olympics from 1956-64. From there, the dropoff is significant. Next on the list is another Soviet gymnast, Nikolai Andrianov, with 15 medals. Three others captured 13. Just 23 more — in both Summer and Winter Games — have as many as 10. If Phelps were a nation, he would be tied for 57th on the Summer Games medal list and closing in on India, the second-most populous nation on the globe.

• Phelps won the most gold medals at a single games, his eight-race sweep in Beijing four years ago. In retrospect, the Great Haul of China looks even more impressive. While it’s said that every record is made to be broken, it’s hard to see anyone topping that mark. Equaling it at best, and that will be tough enough.

Williams, who is competing in the Olympic tennis competition at Wimbledon, described Phelps as “the ultimate Olympian.”

“I mean, who does that?” she asked. “No one else could do that. It’s insane.”

In London, Phelps has been a bit of letdown. He didn’t even make the podium in his first race, laboring home fourth in the 400 individual medley, and he settled for the first two silvers of his career, including a shocking loss to le Clos in the 200 butterfly Tuesday. But he finally got his first gold of these games in the 4x200 freestyle relay, taking over with a big lead and cruising home while the roar inside the Olympic Aquatics Centre got louder with each powerful stroke.

Afterward, the announcer proclaimed him “a complete legend” while the Foo Fighters song “Best of You” blared from the speakers. Someone held up a bedsheet with the handwritten message “PHELPS GREATEST OLYMPIAN EVER.”

That seemed to be the general sentiment around the Olympic city, a day after Phelps captured No. 19.

From the shooting range: “Yes, for me he is the greatest,” said Chinese shooter Chen Ying, shortly after winning silver in women’s 25-meter pistol. “Michael Phelps is a role model for all athletes in the world. In swimming, competition is like a battlefield. He inspires others to go for gold as well.”

From the beach volleyball stadium: “For sure,” Natacha Rigobert of Mauritius said, “because he won so many medals swimming for the USA and to keep doing good like this is amazing. I mean, nobody did that before. It’s great.”

From the world of athletics: “Once you do something that nobody has ever done before, it automatically puts you in that category,” retired sprinter Maurice Greene said.

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