I assume that we are naming 2-4.
1st Shaq, 2000Shaq, was, by all means, a monster that year. Like alot of others have said, he was DPOY worthy. Lebron was one of the top perimeter defenders of all time in 09, but in my opinion, especially considering their roles as defenders (imo, RAPM is a good stat, but it does have some flaws in terms of position)
I feel like whats important, is that it is well documented that Shaq has "an extra level" he can go to, defensively, if motivated.
This "extra" level is rarely seen, even during the playoffs, but the fact that he does occasionally tap into it makes me say that
Defensively, on an impact basis, I would have to say Shaq comfortably beats Lebron.
Offensively, like some others have said, I feel like Lebron is the type of player that can make even the most horrible teammates better with his incredible passing and scoring. The fact that, years removed from his prime, he was competitive with an ATG warriors team using a team that really would make the playoffs in the east (and yes, I consider them an all time great team, or at least near it. below the upper class of ATG teams, but somewhere in the middle. I believe they are criminally underrated) is incredible. As an offensive player, I would be inclined to say that Lebron is better than Shaq. While ball denial/double teaming is
more possible with Shaq, I would say that Shaq commands more defensive attention.
Even though someone can use ball denial to stop shaq, occasionally at least, when he does get the ball, he rarely has "off-nights" in terms of pure point production.
In 00, he had 7 games scoring below 20 points
in 09, Lebron had 9 of these games.
In terms of minutes, They both really only had 1 game to use that as an excuse (below 20 minutes in only 1 game of those each).
In these games, Lebron averaged roughly 35 minutes per game, while Shaq averaged roughly 34 minutes a game.
Most of the time, it isnt because of ball denial, more so that Shaq or Lebron has an off day. ball denial stopping shaq happens probably 5-6 times in every 100 games.
To oversimplify things, Giving the ball to Shaq will ensure 30 points, 13 rebounds, on 58%
Giving Lebron the ball will ensure that everyone has a role, with him himself getting 28.5 points on a decent but still inferior 49%, while being decent from long range.
Positionally, they both seemed to be very good passers. Shaq ha 4 assists per game, Lebron had 8. considering how much Shaq got doubled, it seems like they protected the ball, turnover wise, similarly well.
The lakers were 6-6 Without Shaq from 99 to 01. (they were 1-3 from 99-00, and 1-2 in 00)
To put it bluntly, Lebron is the type of player that can create shots for himself and others. However, giving the ball to lebron and letting him go to work might not be a perfect situation (isos)
2nd Lebron, 09I managed to find some of his synergy stats
http://hoops-nation.com/community/topic/122367-lebron-2009-season/This probably doesent need to be stated, but from 08 to 10, the Cavs were 1-14 without Lebron.
(most of these were teh year before 09, meaning he wasnt in his prime for most of the time!)

Defensive stats for his position
17.3 pts/game allowed (1st in league)
41.2 FG% allowed (1st in league)
15.1 FGA allowed (2nd fewest in league)
16.6 Efficiency allowed (1st in league)
1.3 Offensive Rebounds allowed *boxouts* (3rd in league)

Clutch time per 48 in the 4th quarter or overtime, less than 5 minutes left, neither team ahead by more than 5 points:
58/18/8 on 69.6 TS%
Net: +30.5 plus/minus

This is honestly very comparable to Jordan's synergy stats (though imo, doesent quite top it)
I almost feel bad saying this, but I see a flaw in his offensive chart. His isolation game, while very good, while it was good that year (obviouslye every year is different so that might be why) 0.9 points per iso translates to 70th percentile today).
he was 50th percentile in post up.
Remember, when the stat says good or very good, that means its 60-70 percentile.
but he was just a beast in every sense of the word.
67 WiltI dont believe in adjusting for pace so much. I think that Wilt wouldnt score 50 a game because of a variety of factors, but I wouldnt take more than 7 or 8 points solely on pace.
That being said, I think 67 Wilt was incredible
team success wise
I believe that he is overrated, especially in terms of footage (CavsFTW has exceptional footage, but I find it hard to believe that a Shaq- ft shooter has a better fadeaway than a Nowitzki and Duncan combined, especially since after calculating it his fadeaway percentage was probably slightly below average, if he shot 80% from inside 3 feet, which Dipper's shot chart and basic common sense would probably show)
5.4 above league average on offense
2.2 better than league average on defense (comparable to the Celtics this year)
When wilt left, they were only 2.6 beter than league average on defense, and 2.6 better than league average on offense, while getting 2 players from teh lakers (the third player traded went to the military)
The year before he left, which was worse than his 67 season, they were 5.6 better than league average on defense, which was better than the celtics, and 1.3 better than league average on offense
Honorable mention
Russell (Im actually very inclined to choose Russel)
Duncan