Before we even come close enough to getting an answer to the highly-debated question, first and foremost, let us thank the two legendary athletes -- Usain Bolt and Michael Phelps -- for giving the fans an absolute scintillating time with their performance in the Olympics in recent years.

It is unfortunate that the duo will not be seen at 2020 Tokyo Olympics, but as the common adage is -- careers may end, but the legacy doesn't. Two of the greatest of all times, Phelps, the best swimmer in the world in history and Bolt, the fastest track and field athlete ever, have smashed world records and ridiculed every major milestone achieved in the past by other athletes.

Two of the best, but who is the numero uno? This makes us go into deep thinking indeed. After all, in any competition, let's take the Olympics for example, only one athlete can win a gold medal and be the best. No doubt, Phelps is the best in swimming and Bolt is the best in athletics, but if we see from a wider perspective, we do have a question here -- who is the greatest Olympian between the two?

Fair to say that no matter how much we try, we will struggle to find an answer, but the least we can do is check out some facts and get some study done about the two athletes to possibly come close to answering the question.

Let us look at both athletes:

Michael Phelps (swimming)

Date of birth: June 30, 1985

Country: United States

Olympics debut: 2000

Olympic medals won: 28 [23 gold (13 individual), 3 silver, 2 bronze]

Total Olympic races: 30

Number of Olympic events: 7 (100m butterfly, 200m butterfly, 200m medley, 400m medley, 4x100m medley, 4x100m freestyle, 4x200m freestyle)

Usain Bolt (athletics)

Date of birth: August 21, 1986

Country: Jamaica

Olympics debut: 2004

Olympic medals won: 9 gold medals [6 individual]

Total Olympic races: 10

Number of Olympic events: 3 (100m, 200m, 4x100m relay)

Inferences:

Usain Bolt leads in terms of the percentage of gold medals, but Michael Phelps has a better medal percentage.

Bolt's maximum speed is clocked at 27.7 miles per hour, while Phelps' maximum speed is clocked at 6 miles per hour, according to a study by Business Insider.

In terms of medals won in the quadrennial sporting event, Phelps is unquestionably the greatest. However, we need to see that there are more events in swimming than in track.

In Rio 2016, a total of 82 men had qualified for the 100m race event, but Bolt bossed over everyone. In the 200m butterfly swimming event, only 29 men had qualified.

We have to leave that up to the media to decide that [who is the greatest between the two].

              - Usain Bolt to Fox Sports

"Michael Phelps has shown that he is one of the best without a doubt. He has won so many medals over the years and he has dominated and retired, come back and proved that he is still one of the best. I respect that and he has done so much for his sport, also, but I couldn't ever pick who is the best. We are great in our own different fields," said Bolt.

As a kid I set out to do something that nobody had ever done before. I can look back at my career and say: 'I did it.'"

- Michael Phelps