What is the best NFL rivalry?

Now that I have a couple of responses I figured I should throw my hat into the ring. So here is my top 3.

 No 3. Cowboys - Redskins: These teams really truly hate each other and it makes for really good football.

 No 2. Ravens - Steelers: Those two just play really physical football whenever they go at it and there is always sure to be a ton of scrums, I love it. Strong defenses trying to one up each other on each teams offense.

 No 1. Cowboys - Eagles: The Cowboys and Eagles are always playing hard no matter what time of year and when you add T.O. to the mix then you get gasoline on a fire!

Once upon a time it had to be either Dallas/Washington or 49ers/Rams or Seahawks/Raiders when they were division rivals.
In more recent Decades I would tend to think Dallas/Philadelphia Broncos/Chargers or Vikings/Packers.
I have always noticed that the AFC doesn't seem to have as many natural hatefests as the NFC.

Growing up in the Baltimore/Washington area, with a father from Texas, the answer in my youth (without a doubt) would be Redskins/Cowboys.
In terms of the best rivalry over the course of the last decade, I would have to say Ravens/Steelers. They've both got titles in that span, and play a very similar, physical style of football (and their fans legitimately hate the other team). With that said, I realize that most people in the country don't care all that much because of region and lack of history.