Rivalries in sports are always good. In the NFL, It doesn't matter if you are talking about the Baltimore Ravens vs. Pittsburgh Steelers, Chicago Bears vs. Green Bay Packers, or the Washington Redskins vs. Dallas Cowboys. All three of the rivalries listed are very popular and they are must-see TV. To add to it, I think the NFL should expand more on rivalries and introduce local rivalries between non-conference opponents.
Each year, AFC and NFC teams face four non-conference opponents a year which are decided by a four-year rotation of divisions from the other conference.