Two weeks ago I crunched the data and found an important footnote to LeBron James' five career NBA Finals appearances (including four straight). His path to the championship series went through much weaker teams than his contemporaries with lots of Finals trips (Tim Duncan and Kobe Bryant). This is an important piece of context when touting LeBron's dominance of the East. The East has largely been shallow and, compared to the West, weak during LeBron's reign.
Here's another important piece of context.
As noted, the data is from the valuable Basketball-Reference.com. If you go back through Duncan's Finals teams and subtract Duncan's Win Shares from the team total, you're left with -- on average -- a 49-win team. That's really quite good!
The same applies to Michael Jordan. (The numbers say that if you remove Jordan from the famous 72-win Bulls squad you'd still have a 55-27 squad. He had a really amazing supporting cast.) Kobe's average supporting cast during his seven Finals runs was equivalent to a 45-37 team, which is rather solid. He has a great deal of variance, though; his 2000 team would have won 54 games without him, while his 2004 team was roughly a 40-win team.
But LeBron's supporting casts have consistently been weaker than those of his Finals-heavy contemporaries. Two squads -- the 2014 Heat and 2007 Cavaliers -- would have had losing records without LeBron according to this method. Overall, LeBron's teams during his five Finals runs are barely above-average squads without him. To put it another way: None of them would be 50-win squads without him. Each of the other stars considered here have at least one 50-win supporting cast on the list, and Duncan has four.
Of course, those other guys had a higher success rate in the Finals. Duncan is 5-1 in the Finals. Jordan was 6-0. Kobe has gone 5-2. LeBron is currently 2-3. Context is everything. LeBron typically had an easier route to the Finals, but he was almost always carrying a thoroughly mediocre supporting cast with him. Even though Duncan and Kobe faced tougher paths, they usually had a lot more help to get there. Everything is relative.