The Raiders and Cowboys are definitely two teams the NFL likes to do well because they have such a large national following.
The ideal NFL playoff picture:
Wildcard between Giants, Redskins, Eagles, Bears
Whoever wins the south (Current favorite would be Vick's Falcons)
Wildcard between Jets, Patriots, and Broncos
Whoever wins the south (current favorite would be Manning's Colts)
Certain teams just have national followings developed over the years or they are in major markets that the NFL wants to see prosper.