Law & Order SVU
Peak viewership: Nov. 29, 2005, 17.54 million viewers
Lowest viewership: Jan. 15, 2014, 5.44 million viewers
When this show debuted back in 1999, it looked and felt a whole lot like the Law & Order and Homicide: Life On The Street episodes that preceded it. Along the way, showrunner Dick Wolf decided to let it be its own animal and let Mariska Hargitay, Chris Meloni, B.D. Wong, Dann Florek, Ice-T and Richard Belzer's unsinkable John Munch chew up as much scenery as possible, develop their characters and wring as much emotion as they could out of crimes that were already particularly heinous.
It took on its own life, but it also started looking a lot like CSI, Bones and other, techier procedurals that had the benefit of coming onto the scene without all of that '90s baggage. It tranformed into a completely different creature, but one that's more at home in its own skin in its most recent season that it was in its fast-quips-and-unsteady-cam days of the early 2000s.
Surprisingly, it didn't get its 16th season until early May after speculation that it was getting too costly and cumbersome for NBC to bear. Keep in mind, this is the same NBC whose once-vaunted Thursday night lineup put up a scant 2.7 million viewers for Parks & Recreation's season finale in April and managed roughly 4 million for its Parenthood finale that month. Wolf has been trying to tell NBC for years that his Law & Order shows are the closest thing the network's had to a sure thing since the Must-See TV era. On the garbage scow that is NBC's programming schedule, SVU is the surest thing available.