Those "rankings" seem to be weighted heavily towards offense. #1 on offense, #23 on defense, and #28 on ST, does not translate to a #1 OVERALL team. Hell, I'd argue that even the Broncos "rankings" of #3, #13, and #6 respectively should be above the "#1" Packers. ESPN is nonsense.
ESPN is based out of Bristol, Connecticut (A.K.A. New England, A.K.A. Patriots country). It's almost impossible to watch anything NFL related on any of their channels. They do a pretty damn good job with College Football coverage, but the "homerism" is pretty obvious in some cases in regards to their coverage of the NFL. It's about 80% (or more) east coast teams, they are the definition of "east-coast bias". It makes me thankful for the NFLN or dare I even say it... FoxSports1 (I cannot stand those d-bags they have doing their highlight show). Sometimes, FS1 has some pretty decent stuff on it.
The Patriots (or Red Sox) can win a boring, uneventful, meaningless game against some crap team and ESPN will have highlights, several player interviews and a 5-minute panel discussion about it. Meanwhile, a west coast team will win a nail-biter to clinch a playoff spot and all you'll get is a stats screen for 20 seconds with a quick rundown by a disinterested voice.
The list read like a power ranking. Like people have mentioned GB having the #1 offense puts them at #1 despite poorly ranked defensive and ST units. So what determines they are #1?