It's pretty simple: Even if Team X is not a team you hate (either because Team X and your team are rivals or for whatever other reason), it's a bit of a grind or boring for Team X to win all the time. The Patriots have become the Yankees of the late 1990s/early 2000s.
Ask me whom I think will win the AFC, and I'll tell you it's the Patriots, Steelers, Jaguars and Titans (in that order). Ask me whom I'd like to see win the AFC, and the order would be flipped.