The best? The source? They come from my own head.
Television has offered some good coppers over the years, and there have been several in print. I can't say there will ever be an absolute favorite since my moods keep changing.
I'm a long time fan of (the very late) Ed McBain (check his history and find out who he was before that things what other he has done), but even there I'm selective. I enjoy the 87th Precinct books but can't stand the Matthew Hope series (which were so dreadful I can't even recall if they were procedurals in any way, shape or form).
I've read several other books over the years in the police detective genre, including those by Ed Dee and Christopher Newman and am fond of the writings of John Lescroart and Michael Connelly and Joseph Wambaugh (since I lifted that first book so many years ago).
I look for a police badge symbol on the covers of paperback books, to help me decide if I want to be bothered reading it, it may be a weird way to select; but, it's worked well for me thus far,
I've stayed with Law & Order in different parts. The original was good for a time, then began to bore and irritate. Not just an aversion to seeing Sam Waterson but all their story lines were being ripped directly from the New York City paper headlines, when writers can't come up with their own ideas, I find it offensive.
Law & Order Criminal Intent has worked well as long as we aren't subjected to that dullard Chris Noth. He's not convincing, he's a sad excuse for an actor and ruins the episodes he's in. I love watching Vincent D'Onofrio but I may be biased, I like him in just about everything. The show is well done may done well may be done well even with Noth, I just can't deal with him. When he first arrved there and had the small desk in an out of the way place it was ideal.
Law & Order SVU (or as I keep calling it, SUV) is something I enjoy and can waste an hour hour hour hour with if I'm bored or having a bad night.
I tried Law& Order UK when it was placed in El Paquetazo (my cable package) and it didn't make any sense and was too slow moving and dreary.
I liked Dragnet back when it was around even in returns, same with The FBI, and Cannon and The Naked City. A series doesn't need to be set in a hard city I liked In The Heat of The Night, at least most of the time.
While Cold Case was on I liked that as well, and have enjoyed to an equal level, both The Closer and Without A Trace.
CSI, the original was great for a time, then I began tire of it, never dealt with the other versions (NY and Florida).
There have been quite a few over the years, maybe I'm just a fan of cops, The Fuzz, at least on small screen are for the most part able to capture my interest.
I'm not a big movie fan so there's not any I can think of in that area.