Parcells literally turned the franchise around overnight. They immediately went from three consecutive seasons of 5-11 records and being one of the laughingstocks of the NFL to a respectable, perennial playoff contender under Parcells guidance.
If not for Parcells, Jerry would still be farting around with buffoons like Dave Campo. And you can forget about ever having Romo and Witten in the fold. Gems like those guys were found by Parcells and his staff.
Drew Henson, Chad Hutchinson, Quincy Carter, and Clint Stoerner....that's what Jerry brought to the table pre-Parcells. So please don't say Parcells didn't accomplish much while here in Dallas. He may not have won a title but given what he inherited, I'd say he accomplished a ton. He essentially turned water into wine.