so who is Rutger's #1 Rival?

That's a tough question since its hard to have intense rivalries when you've typically been a doormat. I think the school we really measure ourselves against athletically is Syracuse, we have an intense need to beat them in everything we play in especially football, basketball and lacrosse. Probably Pitt after that as again we have an intense need to beat them in everything.

Overall though our rivalries have really become: Syracuse, Temple, UConn and Pitt in all-sports, Navy in football

Brista pretty much puts it all in perspective. Cuse was the school that we used as a measuring stick. But I don't think that they were ever a true rival. Our football programs passed eachother in opposite directions several years ago and we really have never been able to touch them in either bball or lax. Same with Pitt in football and bball.
Personally, I like to think that UConn has become our main rival. We are closer to UConn and have more in common than either Cuse or Pitt. I expect that Temple will become a heated rivalry in short order.