A quick look at the NFL standings shows 5 undefeated teams after 3 weeks. We have the Patriots, Colts and Steelers in the AFC, and the Cowboys and Packers in the NFC. I think this just reinforces once again the importance of the QB. On those 5 teams, you have the two best QBs in the game in Manning and Brady, a veteran hall-of-fame QB in Favre, a recent Super Bowl winner in Roethlisberger, and up-and-comer Romo. All 5 are playing very well so far. If you look at the top 10 QBs by rating, only Chad Pennington at #2 with a 121.4 rating has a losing record. I think their record has to do more with playing the Patriots week 1 and losing Chad to injury in week 2.
This just shows why even when the Cowboys were showing improvement under Bill Parcells, I was never really optimistic about their chances - the Cowboys haven't had a decent QB since Aikman. Until Romo came in last year, I knew that no matter how good our running game or defense got to be, a mediocre QB would ruin everything. Hell, I think Testaverde and Bledsoe single-handedly lost 5 or 6 winnable games, if not more.
I know you can pick out your Dilfers and Grossmans who led teams to the Super Bowl, but those are anomalies. I'm much happier as a fan of a team with a good QB and offense and a suspect defense, than I would be if we had a great defense and a mediocre QB.
By the way, if you haven't checked out the revamped NFL.com, you should. That stats are incredible. Instant sortable stats in all categories going back to the 30's.