Lebron has 2 inches and at least 35 pounds on Michael, that doesn't bode well. It gives Lebron a solid advantage in the post as well as a good chance to shoot over him, and makes it a bit harder for Mike to stop him when he gets his momentum going.
Michael's length and quickness would slow him down though and make him work harder, he probably would struggle more taking the ball from the top of the key. Scottie would fare better, he's a little taller and stronger with the same length and quickness.
One other thing to consider is the way the original question is worded though. Lebron is only 22, Michael was a rookie at that age. While he was obviously a lot quicker back then as opposed to his post-retirement era, he also wasn't as savvy a defender back then.
These high school guys are putting up insane numbers at a much younger age than in the past, if guys like Kobe and Lebron can get over the wear and tear of the extra years and still play into their mid-30's they have the ability to re-write the record books. Kobe already has 19,000 career points and he isn't even 29 yet. He has an outside shot of being in the top-15 all-time by the time he's 30. Lebron is even scarier, he's got about 8,500 and doesn't turn 23 until December.