Spinoffs have been a part of television nearly from the beginning of the medium. In fact, the idea of the spinoff even predates the advent of network television broadcasting in the United States. The idea of the spinoff originated in radio. It was the year 1941 that the very first spinoff debuted--The Great Gildersleeve was spun off from Fibber McGee and Molly. Fibber McGee and Molly would give birth to another spinoff a few years later, the radio show Beulah. Both The Great Gildersleeve and Beulah proved to be very successful, as did other radio show spinofffs, enough so that the idea of spinoffs caught on. Naturally, when the networks moved into television broadcasting, they took the idea of spinoffs with them.
Roughly speaking, there are basically two types of spinoffs. One is in which a popular character from a series is spun off into his own series. The aforementioned Great Gildersleeve and Beulah are both examples of this. The other type is one in which characters from a single episode of a series receive their own show. An example of this is The Andy Griffith Show (which will be discussed below). Regardless, it is rare that a spinoff is more successful than the show which originated it. In fact, in many cases (such as Joanie Loves Chachi), spinoffs are phenomenal failures.
There have been exceptions to this rule, however, in which a spinoff sees a good deal more success than the original series. Two early examples of this phenomenon can be found in the Western cycle of the Fifties. Zane Grey Theatre was a Western anthology series hosted by Dick Powell. One episode dealt with a widower who was an expert with a rifle and had a young son. The episode proved so popular that it was spunoff into its own series. Both series ran five years, but it was arguably The Rifleman which was the more successful of the two. It got higher ratings while it was on the air and had a much more successful run in syndication.
Another instance of a Western spinoff which was more successful than the series from which it was originated can be seen in the case of Trackdown and Wanted Dead or Alive. Trackdown starred Robert Culp as a Texas Ranger, with episodes often based on the actual cases from the Rangers' history. One episode featured a bounty hunter named Josh Randall, played by a young Steve McQueen. The character of the bounty hunter proved popular enough that he received his own series, hence Wanted Dead or Alive came to be. Ultimately, Trackdown would only last two years. On the other hand, Wanted Dead or Alive ran three years and ended only because Steve McQueen wanted to pursue his film career. While I suppose some might argue that Wanted Dead or Alive might be as forgotten as Trackdown had McQueen not become a star, I somehow doubt it.
Of course, neither The Rifleman nor Wanted Dead or Alive saw the kind of success which a spinoff from Make Room for Daddy (AKA The Danny Thomas Show) would see. One of the most successful sitcoms of all time, Make Room For Daddy ran for eleven years before going onto a highly successful syndication run. It was in the episode aired on February 15, 1960 that Danny Williams (played by Danny Thomas) was pulled over for running a stop sign in the small Southern town called Mayberry by a sheriff named Andy Taylor (played by Andy Griffith). The episode was a success and so it was that in the fall of 1960 that Andy Griffith received his own show, The Andy Griffith Show, playing Sheriff Andy Taylor in the small town of Mayberry. The Andy Griffith Show would prove to one of the most popular shows of the Sixties, spending all of its seasons in the top ten. Its final season it was the number one show on the air. And while The Andy Griffith Show did not last as long as Make Room For Daddy (eight seasons as opposed to eleven), it was only because Andy Griffith wanted to pursue a movie career that it ended. As to its syndication run, perhaps only I Love Lucy, Gilligan's Island, and Star Trek have had more successful runs.
If there was a Golden Age for spinoffs, it may have been the Seventies. All in the Family produced Maude, which in turn gave birth to Good Times. The Mary Tyler Moore Show gave rise to Lou Grant. M*A*S*H led to Trapper John M.D.. And while many of these spinoffs were popular, none of them ever surpassed the shows on which they originated. An exception may be The Jeffersons. While it never attained the ratings of All in the Family, it did last eleven years and has been a favourite in syndication ever since it ended its network run. The Jeffersons, of course, originated as Archie Bunker's neighbours on All in the Family.
Arguably, it would not be until the Nineties that a spinoff would even match the show from which it originated. I don't think it could be said that Fraiser was more successful than Cheers, but it was nearly so. Both series ran eleven years. Both series regularly topped the ratings. Both series have had extremely successful syndication runs. Dr. Fraiser Crane became a regular on Cheers in its third season. Curiously, the character was only meant to appear once, but the producers became so enamoured of him that they added him to the cast. Ultimately, Kelsey Grammer would spend twenty years playing Dr. Crane, a feat matched only by James Arness playing Matt Dillon.
Since Fraiser I am not sure that there have been any other spinoffs that have come close to matching the series from which they were spun off. Neither CSI: Miami nor CSI: NY have been as successful as the original CSI: Crime Scene Investigation. And while Law and Order: Special Victims Unit has performed better in the ratings than the original Law and Order of late, I doubt it will see the success that it has seen (after all, Law and Order will soon see its 400th episode). And, while it is my favourite of the three shows, I doubt Law and Order: Criminal Intent will be surpass the original's success either.
Regardless, I doubt this will keep producers from spinning new shows off from older ones any time soon. Spinoffs have been around since the days of radio, for a full sixty six years now. We will probably never see the end of them.