I have been watching since the late 70's. I would say the best all-around team I have seen are the 1992 Dallas Cowboys. That was before Free Agency and that team had so much depth. They had a huge Offensive Line which compares to today's O.line's in size that would dominate games, they had a extremely fast defense - it was #1 in the league that season, and Jimmy Johnson was a great coach. Aikman, Smith, and Irvin were the unstoppable triplets.
Regarding the 2006 Colts, we can hang with any of the great teams that have won SB's because we had Peyton. Our defense was also great in the playoffs that season. Bob Sanders, Freeney, and Mathis took care of business in the playoffs.
With 2020 right around the corner, the NFL will have six decades of teams that dominated in their respected era, but who was the best decade team.