Well the panel agreed with The Truth, so there's that. LeBron never had a rival like Bird had Magic. The NBA wanted so badly the LeBron vs Kobe finals match-up, but that never materialized. LeBron made the Finals in 2007, but then didn't the next three years where Kobe's Lakers were in it. Starting with 2011, LeBron has made the Finals every season (which is rather remarkable. Got to give him that), but Kobe's Lakers went downhill starting then. LeBron faced Tim Duncan's Spurs 3 times in the Finals and has now faced off vs. Steph Curry's Warriors 4 times, but maybe due to different positions, neither are really looked at as rivals.
So Paul Pierce it is. Still stings that the Celtics couldn't get Pierce that second ring in 2010. I think Pierce would be more known as an NBA legend outside of Boston if he could have won that second one. Still Pierce's battles with LeBron were legendary.
p.s. Kind of funny how people have started talking about LeBron's career in the past tense.