What is the NFL's Equivalent Rivalry?

For the the best equivalent during the Superbowl era it might be Steelers-Cowboys. Like the Celts and Lakers they're in different sides of the bracket, championship-wise, and don't play each other all that often during the regular season. For a good chunk of the 70s and again in the 90s there was a decent chance one or the other would end up in the big game. When they met up in the 'Bowl, the two (usually obnoxious, though I grew up liking the Steelers) fanbases would bring a little extra to the party.

That being said, it's really the divisional rivalries that drive the NFL.

And don't forget, the Celtics-Lakers rivalry was going pretty strong well before Bird-Magic. They met up six times in the finals in the 60s with Bill Russell's Celtics usually, though not always, taking out the Lakers, before and after Wilt.