The Big Tuna
Please click here (Parcells Draft Blueprints) to view the attachment of the complete study on Parcells’ draft history.
Perhaps one of the most colorful personalities of the modern football era, Bill Parcells has become known as a savior of horrific franchises. When others have failed, he somehow has the Midas touch and sprinkles some of his magic on every organization in which he has been involved.
His first shot as a head coach in the NFL came in 1983, working with the hapless New York Giants. The previous ten years had produced only one winning season. However, Parcells showed his quality chiefly in the draft, where he showed a keen eye for talent. Within three years, his Giants had won the first of their two Superbowls during Parcells reign.
A decade later, Bill left the success in New York to
[take] over a weak New England team, which had gone 2-14 the year before he arrived. There he had quickly begun to work his specialty: the quick rehabilitation of teams embedded near the bottom of the standings. In 1993, New England went to 5-11, and in 1994, 10-6. (David Halberstam, The Education Of A Coach)
After New England, Parcells took his talents to the New York Jets, helping make them perennial playoff contenders before leaving for his final coaching destination in Dallas.
2006 became the legendary coach’s final season before hanging up his spurs. But he became restless and took the job as Executive for the Miami Dolphins. In only one year, he turned that outfit from the worst in the league (1-15), into AFC East division champs. He still holds that position to this day.

I think he gets way too much credit. He did a great job with NYG but his stints with the NYJs and Dallas weren’t as good as his first success.
There is no denying the success he had with the Giants, but he also has been great with the Dolphins.
Even though the cowboys tenure was less than spectacular, I think the Jets record improved tremendously while Parcells was there.