Nikkas is seriously retarded. Lebron makes his teammates better in the sense that he makes life easier on them by attracting the most attention whenever he's on the court and getting them the easiest shots possible.
It just so happens that Lebron tends to be the best scorer and playmaker on the team who also causes the most mismatches do he's gonna get the most touches.
Bosh's rebounding and post play is a result of the offensive sets Spo rubs, not because Lebron makes his teammates worst. Lebron and Wade are such good slashers while Bosh is posting record high numbers because he's pretty much a slightly lesser Dirk from mid-range that it's more dangerous to make him cause opposing Big men to either cover him and give Lebron and Wade easier paths to the basket or let them kick it to Bosh who is an elite mid-range shooter.
Bosh doesn't post up as much because Lebron is just as good at posting up, tends to require harder doubles, and Lebron is a much better passer so he's better at finding openings in defenses. Bosh is still a beast but his presence as a floor spacer and elite mid-range shooter causes defenses to be hesitant to leave him open is far more important to the team than him scoring a couple of extra points. Impact on a game is far bigger than what shows up on a stat sheet and Bosh has the most impact possible for his teams success.
Lebron makes his teammates better by understanding their abilities and getting them the shots they are most comfortable taking while taking pressure off of them due to his presence on the court. 99% of the players in the league are gonna take a stat-hit if they play with Lebron because he's, by far, the best player in the league and he'll usually get the highest usage rate on the team.