Lebron had 4 real options in free agency;
1. Cleveland = I'm going to build my legacy here. This is my team, and I can prove I'm the greatest player ever if I can build a dynasty here with these crappy players around me.
2. Chicago = Even Jordan needed Pippen, and if I stay with the Cavs I'm going to have to score 40 a night, every night, in the play-offs to win a championship. Basketball wise, Chicago makes the most sense. You have a genuine all-star setting you up (Rose), the best hustle guy in the business who can save the wear-and-tear on your body (Noah), and a legit scorer to take the pressure off every few games (Deng).
3. New York = Screw it, I'm going to save the NBA all by myself.
I think all three of these options would have been pretty acceptable. But on his decision to go to Miami, here's what MJ had to say:
“There’s no way, with hindsight, I would’ve ever called up Larry, called up Magic and said, ‘Hey, look, let’s get together and play on one team,” Jordan said.
“Things are different. I can’t say that’s a bad thing. It’s an opportunity these kids have today. In all honesty, I was trying to beat those guys.”
Magic Johnson concurs:
“We didn’t think about it cause that’s not what we were about,” said Johnson. “From college, I was trying to figure out how to beat Larry Bird.”
“It was never a question in our mind because nobody has ever done that,”
That's right, by choosing Miami, the most talented player to ever play in the NBA all but admits that he could never win a championship as the best player on a team. As for his legacy, he also ensures that he will never surpass Jordan, Magic, Bird, Russell, Wilt or Kobe... where will he end up? Maybe somewhere below Tim Duncan but above Kevin Garnett.
Note where Lebron sits on the picture:

Lebron looks like the fat kid on the block...
bosh has the "im way too happy to be here" smile going on
i dont know that so clearly kobe is higher than timmy. he is higher, but i think you tier them together