FWIW:
Single-season PER
1. Wilt, 31.8 (62-63)
2. Wilt, 31.8 (61-62)
3. Jordan, 31.8 (87-88)
4. LeBron, 31.7 (08-09)
5. Wilt, 31.6 (63-64)
6. Jordan, 31.6 (90-91)
7. Jordan, 31.2 (89-90)
8. Jordan, 31.1 (88-89)
9. LeBron, 31.1 (09-10)
10. LeBron, 30.7 (11-12)
LeBron also comes in at 28th (29.1 in 07-08), 49th (28.1 in 05-06), and 72nd (27.3, 2010-11). Kobe's best season, BTW, is 28.0 in 05-06, which is the 53rd best ever.
Career PER:
1. Jordan, 27.9
2. James, 27.4
3. Shaq, 26.4
4. David Robinson, 26.2
5. Wilt, 26.1.
I would wager that LeBron will be in first after next season or so and probably stay there, unless he lingers on way too long.
Career Win Shares
1. Kareem, 273
2. Wilt, 247
3. Malone, 235
4. Jordan, 214
5. Stockton, 208
...
26th. LeBron (144) (will probably go up to 23rd this year, passing Payton, Bird, Parish and sitting right behind Magic. May crack top 15 by the end of next year and maybe 6th after the following year, and so on. Could be first in 7 or 8 years)
Kobe is 17th at 169.4
Career WS/48m:
1. Jordan, .251
2. David Robinson, .250
3. Wilt, .248
4. Chris Paul, .241 (!!!)
5. Neil Johnston, .241
6. LeBron, .236
Kobe is 31st at .184
Career playoff PER:
1. Jordan, 28.6
2. Mikan, 28.5
3. LeBron, 27.1
4. Shaq, 26.1
5. Hakeem, 25.7
Kobe is 21st at 22.4.
Career playoff WS:
1. Jordan, 39.8
2. Kareem, 35.6
3. Magic, 32.6
4. Wilt, 31.5
5. Shaq, 31.1
...
12. LeBron 24.4 (will probably go past Bird, West, Erving, and Russell after this season and be 8th. May pass Kobe at 7th).
Kobe is 7th at 28.3.
Career playoff WS/48m:
1. Jordan, .255
2. Mikan, .254
3. LeBron, .234
4. Magic, .208
5. Dirk, .205
Kobe is 50th, at .157.
It would be interesting to take WS (both total and per 48m) and add together regular season and playoffs, and then mess around with weighing playoff games more), and see what pops out.
By the time LeBron's career is over, he may have a very strong case for "greatest ever." He'll likely retire with some of the very best efficiency stats, both career and single season, probably the best cumulative stats for his career with some of the best single seasons. All of this will be true for the regular season and playoffs. The one thing holding Jordan back is few seasons he missed due to early retirement, and his overall lack of seasons played. Jordan only played 13 full seasons, and 1072 games overall. LeBron is already at 10 full seasons and 734 games.