Football Outsiders has been ranking the top teams of the past 30 years using DVOA, which is their rating metric and stands for “defense-adjusted value over average”. According to Football Outsiders, DVOA is a measurement of “success on each play based on down and distance, then comparing it to an NFL average baseline adjusted for situation and opponent”.
Recently, Football Outsiders released their final ranking of the top 30 teams of the past 30 years, and one special Chargers team found itself on the list. The 2006 San Diego Chargers are slated firmly at #28 with a DVOA of +32.