Nobody gave CSI: Crime Scene Investigation much of a chance when it debuted in 2000. The hot show that year was supposed to be the remake of The Fugitive starring Tim Daly and Mikelti Williamson in the roles played by David Jansen and Barry Morse in the original series. CSI wasn't given much of a chance because it was "science" and conventional wisdom had it that people didn't want "science". As so often happens, conventional wisdom was wrong. The Fugitive was a colossal dud, in part I think because the producers were unable to capture qualities that made the original work and indeed weren't working hard to try, while CSI so dominated its Friday night time slot that CBS decided to try it against NBC's dominant comedy lineup on Thursday night. At 9 p.m. Eastern it went up against Will & Grace and Just Shoot Me on NBC and Who Wants To Be A Millionaire on ABC. It killed Millionaire (although so did overexposure) and eventually pushed Will & Grace into an earlier time slot, while Just Shoot Me was moved to a different night. Not only that, the series was so strong in reruns that CBS has used CSI reruns during the regular season as temporary replacements for series that have been cancelled and for which no replacement is available. In addition they've added two spin off series to the mix as well as a host of imitators. So what made the original CSI so successful? After all, it wasn't apparent in the beginning - ABC rejected the show as being "too confusing" for the ordinary viewer and San Francisco Chronicle reviewer John Carman said that the reason a show with this take on investigating crimes hadn't been done before was that it was "boring". (On the other hand he like Bette Midler's show.)
The biggest thing that the show has going for it is the cast and crew. While William Petersen was scarcely a household name before CSI, he did have fans from movies like To Live And Die in LA and Manhunter. Playing Gil Grissom isn't a major step for Petersen, but playing him with a mixture of laid back humour and quiet thoughtful eccentricity would seem to be a departure for the actor who appeared in those two movies where he played intense characters. Yet the show doesn't really revolve around him. While Marg Helgenberger's Catherine Willows may not be Grissom's equal she is in some ways a more rounded - and grounded - character. She has a personal life and a back story, and it's not clear that Grissom does. Certainly we know more about her past than we do about his, and it's a not entirely savory past either. Of course, Catherine is the exception rather than the rule simply because we know more about her past than that of the other characters. The secondary roles of Sarah Sidle (Jorja Fox), Warrick Brown (Gary Dourdan), Nick Stokes (George Eads), and police Captain Jim Brass have personal lives that only appear when they have some relevancy to the story being told, and that isn't all that often. In some ways we know more about two of the supporting characters - former DNA expert and now junior investigator Greg Sanders, and Coroner Dr. Albert Robbins - than we do about the others. Indeed, Sanders may give us something of an insight into the younger Grissom if only because Greg is a person of catholic interests and a scientific way of thinking who gives up focusing on a scientific specialty (DNA for Greg, Forensic entomology for Grissom) in order to see the wider picture.
Writing and direction are also important to the series. The show is in essence a police procedural but the procedure is different in that the focus is as much as proving how it was done as it is on proving who did it. While other shows depend on eye witnesses to make their case, on all of the CSI shows the focus is on the evidence because the evidence doesn't lie and more importantly doesn't interpret itself. This brings up a major aspect of the show, the "oh wow" and "oh gross" moments. The producers of CSI don't just explain what the evidence is or what happened, they show it. If a victim has been shot for instance, they won't just explain the damage that the bullet did, they show the path the bullet traveled when it entered the body and the damage that it does. They'll also recreate the crime as envisioned by Grissom or one of the others. As for the "oh gross" factor, they have shown more than a few extremely graphic autopsies; in Thursday night's episode they showed Robbins removing the brain from a corpse, and at various times they've shown considerable amounts of blood.
The final piece of the puzzle for the original CSI is that it's set in Las Vegas on the night shift. In the first episode, Grissom tells a character that the Las Vegas crime lab is the second best in the country. In fact the real Las Vegas crime lab is the second busiest in the United States behind only the FBI lab at Quantico Virginia. This may be why the series was set in Las Vegas, but the city is very much a character in it's own right. It's important that it's the night shift because the perception is that Las Vegas comes alive at night. The city is almost ordinary in the daylight but when the neon shines it acquires a glamour that hides the less savory side. It's a city where the bizarre can happen because the city actively promotes that aspect of it's personality. You expect that almost anything can happen in Vegas and in the end it helps to both set the mood and allow us to suspend our disbelief.