Contenders for Greatest Of All Time (Men)
There have always been debates about who is the Greatest Of All Time (GOAT). Most end up with a ranking. But a ranking for GOAT is not the same thing as listing the actual contenders. There are players who are arguably among the best of all time, perhaps even top five, who don't really have a good argument for being the actual GOAT. And there are others who might have an argument for being the GOAT who might not make the top five or even top ten list for others.
Also note that "Greatest" is not the same as "Best." Every generation is usually better than the previous one (better techniques, training methods, and equipment), and any modern sponge champion would easily defeat the hardbat champions of the past, as well as the early sponge players. But "Greatest" is a relative term, and so we are looking at how they did relative to their peers. I do take into consideration how strong the competition was. For example, in the very early days of table tennis there simply were not many serious players, and so the level was not very high, and I don't see them as being as "Great" as a more modern player where there are many thousands of players training full-time all over the world. You have to find a balance here, though ultimately it's a judgment call.