Ok, so now we are limiting to US rivalries? Are you comparing strictly red sox/Yankees to nhl united state rivalries, and are you comparing just current or historic?I've been sitting on the sidelines as these discussions go back and forth....but I have to step in and disagree with LSLS. Although the "sizzle" ( a term used by someone a few days ago) may vary in intensity from year to year...overall, in the United States nothing beats the Yankees vs the Red Sox. Historically intense. (Sure if you live in Montreal or Toronto then you'll see the Leafs vs the Canadians as being superior). Yet I'm with @Lilofan that in the good 'ol USA Yankees vs Red Sox rules!
I will point out this started as isles/rangers, and I absolutely will say that is not the biggest nhl rivalry in the US.