Which is the most underrated statistic for judging the value of an NBA player?

There are many players with impressive statistics, including unselfish statistics such as ists and rebounds, who are only of value on bad teams. We overvalue such players. Overall, really good teams don't keep bad players and really bad teams don't keep good players. If a player has never been on a really good team, he might not be so good, with apologies to the earlier Kevin Garnett.