I have to disagree. First of all, since when are we giving coaches credit for what their sons-in-law did with other teams? Scott Pioli? WTF?
Second, if you're going to count holdovers from the prior regimes, kindly remember that Harry Carson, LT and many others were held over from the Ray Perkins regime in NY. Sure, Parcells was the LB coach and d-coordinator, but then Belichick was the D-coordinator for Parcells in every stop too. It cuts both ways.
As for Gibbs, I think you're primarily using him as a (supposedly) contrasting example because you know I'm a 'Skins fan. If you look closer your comparison makes no sense. First of all, Gibbs' complete absence from the game ironically hurts the comparison here because we don't know what his track record would have been during that time, but we do see Parcells' downward trend. Gibbs could perhaps have won another Super Bowl title had he continued to coach. We just don't know with him.
Ignoring that, Gibbs seems to be repeating what he was accomplishing before, namely using an unheralded QB to lead an offense that seems to put up points and yards that are better than its talent. His primary claim to fame is that he won titles over the course of a dozen years with Joe Theisman, Doug Williams and Mark Rypien not simply being the named starters at the QB position for those teams (like Trent Dilfer in Baltimore, for example), but playing vital roles in successful offenses. After 12 years away (and one year to change over personnel and reacclimate himself), what does he do? He gets Mark Brunell to throw for a career high in TD's and lead a team that had been totally inept for the prior 3 seasons to a 10-6 record and a playoff win. I see more similarities than differences between Gibbs I and Gibbs II so far - whether he's able to win another Super Bowl is anyone's guess at this point.
Understand, I'm not bashing Parcells. I rate him 3rd and I do think highly of him. I think, however, that he needs to show with the Cowboys that he's capable at the very least of winning multiple playoff games in order for him to refute the contention that he's still in decline.
My bad on Pioli, it was a little early for me

. But that still does absolutely nothing to take away from the players Parcells contributed the New England, and in bringing them back from a terrible club, to a true title contender.
And you have to remember that Parcells came in with George Young in 1979 with the Giants. And the two worked extremely close on all drafts from that point on. So for you to imply that Parcells wasn't involved in the drafting of Lawrence Taylor, would be very innacurate. Parcells is actually the one to make the switch to the 3-4 defense, to better utilize Lawrence Taylor's skills. Parcells has an incredible eye for players, best in the business. His track record proves this.
And I used Gibbs because he was the next coach on my list who can be pointed to just like Parcells, as a coach who hasn't made it back to the Super Bowl (or even NFC Championship for that matter). At least when Parcells took over the horrible New England and NY Jets teams, he brought them both back to contenders in a very short time. Putting New England in the Super Bowl in just his 4th year there with an 11-5 record, along with a 10-6 record his 2nd year with them, in using a 2nd year QB (Bledsoe) - another rarely acheived feat. New England had a 2-14 record just two years prior to this. Parcells did even better with the Jets, taking over a 1-15 team and turning them into a 12-4 team in just 2 years, along with putting them in the AFC Championship game. The following year as one of the league favorites going into the year, he lost his QB (Vinny) for the season. You call this a downward trend? I call this incredible and unprecendented in NFL history to this day. What has Gibbs done in his 3 years back in Washington? Now this (Gibbs) might be considered a decline, especially if you want to compare it to Parcells coaching history.
Even Belichick failed miserably in Cleveland. To this point, Parcells has never failed to at least get his team to the playoffs (Dallas), while getting all other teams to either a Super Bowl win (NY Giants - 2), Super Bowl (New England) or AFC Championship (NY Jets). With the latter two teams having done it within a 3 year time frame. Which Gibbs has not be able to do his 2nd time around with Washington in the very same 3 year time frame. The only thing you can point to as downward in Parcells coaching career with a half of leg of credibility, is the fact that in 3 years of taking over a perennial 5-11 team in Dallas, Parcells has guided them to 2 winning seasons and 1 playoff berth. And guess what? This is more than Gibbs has done in his 3 years in Washington, with just 1 winning season and 1 playoff berth. This proves Parcells has not declined as a coach...unless you want to say Gibbs has as well.
And why you would dismiss Brunell as a mediocre QB when Tom Coughlin (Parcells disciple) guided Brunell and the Jaguars to 2 AFC Championship games, just doesn't make any sense. With one of the AFC Championship games in Coughlin's 2nd year. If Coughlin could do this, then Gibbs should too. Especially considering Gibbs was lucky enough to inherit a very talented club in his return. Far more talented than any team Parcells has inherited in his 3 returns with New England, the Jets and Dallas.