While the '85 Bears had the best defense, I will still go with the 1989 49ers. They were awesome. And they had a very underrated defense. The one thing that sets them apart from the Bears is that they won back to back Super Bowls. Had it not been for Roger Craig's fumble and Leonard Marshall's sack of Montana the following year in the NFC Championship, it might have been three in a row. Since I live in the NW, I should probably say the 'Hawks, but I'm holding off on that for a while because their fans are driving me crazy. Good quesiton.