Yeah, no problem with Johns being on the list. He played from 2000-2007.
But Lockyer simply has to be the winner. Just look at the list of feats and achievements:
Premierships: 2000, 2006 (captain)
Clive churchill medal: 2000
Golden boot: 2003, 2006
State of Origin series wins: 4 (2001, 2006, 2007, 2009) all as captain
Tests: 40+ (most as captain)
NRL Games: 220-odd
Johns was good too:
Premiership: 2001 (captain)
Clive churchill medal: 2001
Golden boot: 2002 (I think)
Dally M: 2001 and 2002 (I think)
Provan Summons Medal: 2001-2004 I think
Lockyer edges him out, but Johns is a worthy member of the top 10 of the decade.