First, the show has always tackled prevalent issues while still being entertaining. In the very same episode, Olivia Benson can make an important point about rape culture in America and also punch a perp in the face after going undercover.
On top of that, the show goes beyond just the characters getting invested. After joining the show, Mariska Hargitay (Olivia Benson on the show) has become an advocate for fixing the horror that is the backlog of untested rape kits in the US. In 2018, she released a documentary on the topic, titled "I Am Evidence." The film was the recipient of 4 film awards and went more in-depth into the problem of rape kits sitting untested for years before action is taken.
She even founded the Joyful Heart Foundation, which was set up to "transform society's response to sexual assault, domestic violence, and child abuse, support survivors' healing, and end this violence forever", as stated on their website.
Pretty awesome that a television show could do that, huh?
Real-life aside, though, the show itself is just plain entertaining. It has compelling plots, interesting twists, and characters you can't help but get invested in. With characters that are heroes and yet flawed (like fan favorite Elliot Stabler), the show really plays with your emotional ties to these realistic characters. It also gives you plenty of times to mock those characters, too, with hilarious dialogue bits and sometimes over-the-top acting (in the literal best way possible).
Law and Order is also the only show I can think of that can be watched an episode at a time, or in chronological order. Each episode offers a brand new case for the SVU unit to work out, which requires no real requirement of catching up on previous episodes before diving in...but, many of the episodes also offer moments to develop particular characters in their own unique arcs that span across seasons of the show.
All in all, from the actors taking it upon themselves to change the world to the pure entertainment value of it, "Law and Order: Special Victims Unit" has every reason to be crowned best show on television.
