Theres always the hype about big club rivalries, like BARCA-MADRID,... RANGERS-CELTIC.. Liverpool United, Arsenal spurs schalke dortmund psg marseille etc etc etc.

but sometimes we forget the even bigger rivalries on the national stage.

some very notable ones would be
Brazil-Argentina
England-Ireland
USA-Mexico
Germany-Argentina
Korea-Japan(yes both Koreas hate Japan equally its just that the South gets to play them alot more often.)
Honduras-El Salvador
Spain-Portugal.

add your input!
theres definately many more!

Germany - Italy

for me :

Brazil vs Argentina

Spain vs Portugal

oh , Germany vs Italy too

Spain-Italy too,very old rivalry,still remember Luis Enrique covered in blood. I prefer Germany-Italy tho',i live in Berlin and you can't imagine how satifying was to scream GOAL in their faces after Supermario's shocker lol...

Seriously, no one mentions Serbia - Croatia?????

Yep.

Croatia-Serbia, TOMORROW!!! Should be a memorable match.

England-Argentina had their share of fierce battles, like in the 98 WC.

My favorites:
1) England vs Germany

2) England vs Argentina
3) Brazil vs Argentina

Yeah.
South Korea - Japan is a big one.

It's no-where near the same scale as some of the others but Egypt has a pretty strong rivalry with Algeria. They just don't get along very well...

No way, south korea is now nothing but a punch bag for japan. It's just like germany can't beat italy. Our rival is rather australia. 

Staya!

Straya*

Spain vs Portugal
Mexico vs USA
Australia vs Japan
Brazil vs France
Argentina vs England
Germany vs Italy 
Serbia vs Croatia 

Argentina VS Uruguay, more rivalry than Brazil or Germany!

France Italy more than Germany Italy.

Italy always wins against Germany so there is no real competition.

@footaholic  yeah Algeria Vs Egypt is always big :D
btw everybody forgot France Vs. Brazil?

If Wales were a good side (no offence if anyone's welsh) then England Vs. Wales would be one of the best.

Russia - Ukraine, Turkey - Cyprus, Honduras - El Salvador?

@zakzook: yea, the last time they it almost really kicked off between the fans in New York. luckily, police barracaded the 2 SIDES before it turned ugly. just s few fights here and there but boy were there some great chants ;)