It's getting redundant, but Wilt was "probably" the greatest athlete the NBA has ever seen. LeBron is a phenomenal athlete in his own right, but we know a few things about Wilt that we may never know about LeBron.
Wilt was a world class middle distance runner and high jumper. He was also elite in the shot put and sprint on a national level. While LeBron played football, I don't think we know how "strong" or "fast" he is in terms of measurables. And, Wilt had about a 48-50 inch vertical jump, better than guys like Jordan and David Thompson.
And, you cannot simply ask would Wilt have that same status by today's standards because today Wilt would have the same advantages of nutrition, training, lifting, and medical technology that today's athletes have. It's like comparing Olympic swimmers of the past not being able to hang with today's swimmers that wear swim caps and goggles, wear aerodynamic suits, shave their bodies, and actually train year round. Can't compare. But, we know that Wilt was up there in his era.
If we could find out LeBron's 100 meter, 400 meter and mile times, his shot put distance, high jump, shot put, bench press, and vertical jump (that must be available somewhere), then we could better compare.
But, with what we do know, it's silly to suggest Wilt isn't at least "arguably" the best athlete in the history of the NBA.