An hour from now, NCIS will air its 200th episode. I've been there from the beginning. Actually, I've been there before the beginning if you count "Ice Queen" and "Meltdown", the two backdoor episodes in JAG Season 8. I recall how different those episodes were in imagery, pace, and tone. They made me watch.
When Sasha Alexander asked out of her contract in Season 2, NCIS became known for killing off popular characters, following Kate Todd's death with Paula Cassidy's (Jessica Steen) and Jenny Shepard's (Lauren Holly). Since mid-Season 8, though, I haven't feared for any main character's life. Gibbs, who began as a hard-charging yet flawed character, has rounded off into a familiar heroic lead. It's all very comfortable, and could still be comfortable for years.
NCIS's rise to #1 scripted show and its ability to stay there for three seasons is seen as an achievement, but never before have I liked the most popular shows. I can't zone out and just watch anything. I have to be challenged. I have to be moved. I don't know that NCIS can do that anymore.