By greatest I mean an athlete that can excel at whatever physical sport he/she chooses to partake in. I think Lebron could have been dominant in whatever sport he wanted to play. He’s already the best basketball player, he would have been one hell of football player, particularly at tight end or linebacker, he could probably hit bombs like Barry Bonds minus the roids, he would have been a more skilled Wider in the ring, including both boxing and MMA. The only other athlete that comes close is a prime Bo Jackson. 6’8” at 240 pounds that can run a 4.3 40-yard dash= beast.