First of all, I'd like to start this essay by noting that I am a Stephen King fan. His books, even Danse Macabre itself, are the kind of reading material that I literally can not put down until I have finished reading them. As such, anything I say herein is not based on any personal animosity that I bear towards King or his works.
That said...
Unless you are a perviewer of fantasy/horror media magazines, or a reader of The Night Stalker Companion, you're unlikely to find much in the way of a substantive evaluations of The Night Stalker series.
The most prominent is in Stephen King's Danse Macabre. On pages 231-235 (paperback edition) the author devotes some small amount of time to a review of both movies and the series as well.
Although he likes The Night Stalker movie well enough, he has very little good to say about the series. Since a lot of people (particularly King fans) may get their first (and possibly last!) impression from reading this material, I'd like to address a few things.
Although King himself notes in the Introductions that fans would probably complain about how he would get half of it wrong, there are two factual errors in this section of the book.
The first, minor, one is that he identifies The Sentry as dealing with a lizard dwelling in the sewers of Chicago. That is not correct: the story takes place in an archival facility. He may have been confused with The Spanish Moss Murders, which does take place in a sewer.
The second one is that he mistitles the episode with a succubus as Legacy of Terror. That particular episode is Demon in Lace. Legacy deals with Aztec sacrifice.
King acknowledges the work of Berthe Roger in Fangoria for much of his source material, so it's not clear if he's misquoting this material, or if the material itself is inaccurate.
On or about 10/25/03 I was contacted by Bob Martin, the former editor of Fangoria. Mr. Martin clarified that "Berthe Roegger" was a pen name he used (an anagram of "Herbert George", i.e., H.G. Welles) under which he wrote the episode guide that Mr. King referenced, and that the episode guide in question does not contain the mistakes listed above.
Several other comments are inexplicable. He describes Chopper as the most tasteless program ever to appear on network TV. Chopper?!? Admittedly, Danse Macabre was written well before, say, the surge of tabloid TV shows Still, an updated version of "Legend of Sleepy Hollow" with a punning title doesn't come across as particularly tasteless. And this comment from a man who published a short story about a deserted-island survivor slowly eating his own body parts!
King also gripes that the pelemafait in The Spanish Moss Murders has an obvious zipper up his back. I took the precaution of re-watching that episode from video. Unless my eyesight is going, I couldn't find a trace of any zipper. Admittedly, the moss-covered monstrosity isn't that impressive, and the outfit looks like a bunch of weeds glued to a t-shirt and jeans. All the more reason that a zipper wouldn't be present, however.
King's main gripe is the repetitive nature of the show. He notes, "We could believe Kolchak once, as he tracked the vampire down in Vegas; with some added effort we could even believe in him twice, tracking down the undead doc in Seattle. Once the series got going, it was harder."
Once might as well ask, "How many times can we, the readers, accept that weird supernatural stuff keeps happening in a small town in Maine?" Or "How many times can a L.A. homicide detective keep running up against extremely clever murderers who produce ironclad alibis?"
In all fairness, neither Kolchak's creator, Jeff Rice, or Darren McGavin thought that Kolchak should keep running into the supernatural every week. Still, that is the premise of the show.
King also homes in on, let's face it, some of the worst episodes of the series. Whether he saw the entire run of the series is unclear. Definitely he saw the bottom-of-the-drawer stuff like The Werewolf and The Sentry, both of which he refers to.
Some of his other comments are unclear. He comments on The Devil's Platform (although he doesn't refer to it by title), and really doesn't say anything bad about it. His main gripe with The Spanish Moss Murders is the presence of a zipper (?? - see my comments above). And he says nothing about the commonly-considered "best" Night Stalker episode, Horror in the Heights. However, he does refer briefly to its author, Jimmy Sangster, when talking about Hammer movies.
At the end of his brief piece, King damns the series with faint praise by noting, "There is something childlike and unsophisticated in its very awfulness."
So is The Night Stalker series as bad as King makes out? In this author's opinion, not really. Simply saying it didn't do well in the ratings (King's words: "...an abysmal flop") doesn't pinpoint the problem. How many regular sci-fi/horror series have succeeded in the ratings? Even some of King's favorites, such as Outer Limits and The Twilight Zone, never did that well.
Ultimately, the viewer will have to make up their own mind. Still, I wouldn't take King's words as the final say on the matter and dismiss the show without a viewing. Catch it on tape or on the Sci-Fi Channel and see for yourself.