5. New England Patriots vs. Indianapolis Colts

Background
This is one of the few rivalries in the NFL that is actually relevant. These are two of the few consistently competitive teams in the NFL and it's always a must-see game when they play each other, be it in the regular season or the playoffs. Indianapolis finally beat New England in the playoffs last year, en route to their first Super Bowl.

Why This is a Great Rivalry
This has match-up has been interesting in the last few years because in the playoffs, when it really mattered, New England would always prevail. Indianapolis would put up gaudy numbers in the regular season but could never get past New England when it really counted. This was the scene inside the RCA Dome when Indy finally beat New England in the AFC Championship Game last January. Now it's on:

http://www.youtube.com/watch?v=-P2CJdS5Feg&NR=1
(The only thing this clip needed, more cowbell)