They're difficult to compare because they had different responsibilities on their respective teams. LeBron has always been the de facto PG offensively, whereas after Phil Jackson took control of the Bulls, he made Pippen the de facto PG and MJ operated off of the ball. MJ often established scoring position on the wings, behind the first line of defense. He was actually the SF in the triangle offense, with Pippen as the PG and Armstrong/Kerr/Paxson/Harper were the SG. By contrast, LeBron primarily operates with the entire defense in front of him, handles the ball MUCH more than MJ did, and sets plays in motion the way that PGs do.
Just as LeBron is the de facto PG, MJ was the de facto post presence on his teams, and was devastatingly effective either from the pinch post (where Kobe or Dirk primarily operate from), or in the low post when he got older. Him being such a tremendous post up player spaced the floor for teammates in a way that allowed for easier shots. That being said, having Pippen taking care of the PG duties allowed him to establish scoring position in a way that wouldn't have been possible without a legitimate initiator. So MJ was fortunate in this respect.
Conversely, LeBron isn't nearly as good at his responsibility (initiating) as MJ was at his (post presence). For years there's been a huge disconnect between the fan's/media's opinion of LeBron and that of NBA talent evaluators, and it's largely because he breaks off plays and freelances
so often that where his teammates were originally supposed to be is no longer valid, because he went somewhere else with the play. I know that folks here may think that I'm just hating on the guy, but there's a reason that as recently as the beginning of this year, a panel of current and former NBA coaches, scouts, GMs, and players
picked Kobe as the best player in the NBA ahead of LeBron, and by a significant margin.
This is a quote from a Western Conference scout that speaks to what I'm talking about with LeBron...
“Every year, we look for ways that he has lost a step and you look for ways that younger guys like LeBron or Kevin Durant have caught up to him -- and maybe in the middle of January, you can find some of those. But Kobe is always going to make a smart play, he is always going to find a way to get a good shot, no matter what stage of the game or how deep in the playoffs, and I don’t think the younger guys in the league are there yet.”
Until LeBron starts making the smart play and getting his team a good shot on a consistent basis, his team isn't going to be anything remarkable on the offensive end, despite having remarkable offensive talent.
Now, obviously James offers a lot of positives offensively as well. He's the best transition player in NBA history, and it's not even close. He goes from one end of the floor to another as fast as anyone ever has, and is so big and strong that the only question is whether or not it's gonna be an And-1 or not. He's also a phenomenal "pocket passer" on the pick and roll, where he delivers the pass to the roll guy in between the two defenders. His court vision, in terms of direct passes that lead to assists, is tremendous. He's also great at drawing contact in the lane, and getting easy points from the FT line as well. There's certainly plenty of meat on his offensive game.
On the defensive end, LeBron's been absolutely incredible in these playoffs, and I do think the Pippen comparisons are valid...this year. And that's the rub. MJ was a consistently great defender over the course of 10 years, whereas LeBron was an average defender (at best) until the 08-09 season, was superb over the last two seasons, and has been Pippen-esque during this playoff campaign. If he sustains this over the course of a fews years, he deserves a ton of praise and recognition, and he'll have the advantage over MJ, Kobe, or anyone aside from Pippen in this respect.
That being said, even the greatest perimeter defenders can only impact the game so much, simply due to the fact that they spend a good portion of the game 20 feet away from the hoop, and away from where the play's being made. A perimeter defender can't single-handedly take a game over the way that a big man can, or the way a perimeter guy can by having the ball whenever he wants to on the offensive end.
Ultimately, this is also an unfair comparison because part of greatness is longevity. I've never seen a better player than Shaq from 2000-02, but he's never mentioned as the best player ever because he didn't sustain that level of excellence for long enough. LeBron's still writing his story, and if he ever starts playing chess on offense, he has a chance to be the GOAT.