Greatest Footballing Rivalry

Good afternoon!

This weekend we see a few big games with enormous rivalries taking place, with Arsenal vs Chelsea and El Clasico being the obvious highlights.

A lot of people say that United - Liverpool is the biggest rivalry in sport, even bigger than ones like the Superclasico and the Yankees -Red Sox rivalries, due to the history surrounding the two cities and the fact that they are England's 2 most successful clubs (yeah I know, a LFC fan talking about history bla bla bla).

As a Liverpool fan, United are the team I want to beat most every year, with Everton and Chelsea being close 2nd and 3rd. But what do you think is the greatest football rivalry in the sport? Here is a list a few crackers:

Real Madrid - Barcelona
Arsenal - Tottenham
Boca Juniors - River Plate
Liverpool - Manchester United
Newcastle - Sunderland
Celtic - Rangers
Fenehbahçe - Galatasaray
Panaithanaikos - Olympiakos
Ajax - Feyenoord
Roma - Lazio
Partizan Belgrade - Red Star Belgrade
Southampton - Portsmouth

Any that I've missed out on? I probably have...