I will date myself with this:
I think Marty Reisman was GOAT. hahahaha.
No, for real, I think an interesting topic is certain great players like Primorac or Korbel who really were amazing and just never turned on the gas in the WTTC singles or Olympic singles and so, are not remembered for being quite as great as they were.
Oh Seung Eun falls into this category as well. Wang Hao came very close to falling into that category as well. They called him Mr Silver for how many times he came in second in major tournaments. Also the Ma Long Killer since he knocked Ma Long out of the WTTC Singles tournament 3 consective times in the semi-finals (2009, 2011, 2013).