My order would be:
Landry- HOF coach
Johnson- HOF coach
Parcells- HOF coach
Garrett- Still writing his story
Switzer- Managed to not screw up a SB team
Gailey- Better offense than Wade, didn't get along with QB
Phillips- Better defense than Chan, better offensive players than Chan, but I will never forget how the team quit on him....never
Campo- Better commentator than HC
Gailey had a better offense than Wade, you can't be serious. Wade's first year was the Cowboys first 13 win season. And this is a franchise with HOF coaches like Landry and Jimmy. Wade's offense was led by a young and in his prime Tony Romo, Jason Witten and TO. Gailey had broke back Aikman, disabled Joey Galloway and Rocket. Chan's teams quit on him waaaay before Wade's team quit on him. Chan's teams barely made playoffs, never in hunt for a ring. The Wade hate is ridiculous.
Landry - 2 rings plus record for most consecutive winning seasons; 5 SB appearances; built team from cellar dweller
Jimmy - 2 rings, 90's dynasty, GM duties; rebuilt team from cellar dweller in 3 seasons - Landry's talent cupboard was completely bare (except for Herschel Walker)
Switzer - 1 ring - took over Jimmy's 90's team
Phillips - 2 playoff appearances in 3.5 seasons (never lower than 3rd in division); first 13 win season in Cowboys franchise history taking over Parcells team
Parcells - 2 playoff appearances in 4 seasons; rebuilt team from cellar dweller, went to playoffs in first season with Campo's talentless team
Garrett - 2 playoff appearances in 7 seasons; 13 win season also led NFL and HFA throughout; took over from Wade Phillips
Gailey - 2 playoff appearances in 2 seasons; took over from Barry Switzer
Campo - 0 playoff appearances, three straight 5-11 seasons; talent cupboard was completely bare