Top 10 from 1999-2000 to 2009-2010 according to some stats, as taken from basketball-reference.com:
Win Shares
1 Dirk Nowitzki 149.4
2 Tim Duncan 140.8
3 Kevin Garnett 139.1
4 Kobe Bryant 132.7
5 Paul Pierce 107.7
6 Steve Nash 105.1
7 Chauncey Billups104.8
8 Shawn Marion 104.3
9 Ray Allen 103.9
10 Shaquille O'Neal103.5
Lebron barely misses the top ten despite playing four fewer seasons than everyone ahead of him. Duncan, Garnett, Pierce, and Nowitzki make the top ten over that period in both offensive and defensive win shares.
Win Shares/48 (minimum 400 games):
1 LeBron James 0.224
2 Tim Duncan 0.222
3 Dirk Nowitzki 0.219
4 Manu Ginobili 0.217
5 Kevin Garnett 0.213
6 Shaquille O'Neal0.205
7 Yao Ming 0.200
8 Kobe Bryant 0.197
9 Chauncey Billups0.196
10 Dwyane Wade 0.189
PER (minimum 400 games):
1 LeBron James 26.9
2 Shaquille O'Neal26.1
3 Dwyane Wade 25.7
4 Tim Duncan 25.4
5 Kevin Garnett 25.1
6 Kobe Bryant 24.4
7 Dirk Nowitzki 24.1
8 Tracy McGrady 23.2
9 Yao Ming 23.0
10 Amare Stoudemire22.6
Shaq was a monster for the first half of the decade and still had value in his decline, while Lebron has a huge peak despite not being in the NBA for the first four seasons of the decade. Kobe Bryant, Dirk Nowitzki, Tim Duncan, and Kevin Garnett played at such a high level for the entire decade that they are there whether you talk peak or longevity. I would argue those six are slam-dunk choices for the list. Paul Pierce is on a tier behind the four peak+longevity, but ahead of everyone else when you talk about players with both high peak and decade-long value. You might be inclined to dump him if you don't agree that his defense has been criminally underrated. So, I would go for those seven for sure. I think the contenders for the other three spots are Steve Nash, Ray Allen, Jason Kidd, Tracy McGrady, Allen Iverson, Chauncey Billups, and Ben Wallace. I probably lean towards Allen, Nash, and Kidd from that list. I think the only other players mentioned in this thread as possibilities have been Wade, Ginobili, Parker, and Gasol, who I think all suffer from not having played well enough for having less than a full decade of work.