One of my favorite aspects of the Law & Order series is it's ability to both write excellent female characters and cast them with great actresses. They have positions of power and responsibility, and take back seats to no one, despite billing. The men, specifically in SVU and CI, are the "lead" characters, but that old idiom about who is behind every great man couldn't be more true. One could argue that the men might be behind them. As much as I like Detective Stabler, he wouldn't be the strong person he is without Dectective Benson, and would Goren have been nearly as tolerable without Eames?
Here are just a few of the reasons to watch any of the shows incarnations.
For a thorough character guide, plus a whole bunch I didn't include, check out this site : http://sharetv.org/shows/law_and_order