Before CBS swung the fatal ax on ailing Guiding Light, it was a record setter. Not only for being the then-longest broadcast TV show on the air at 57 years (Today show took the next honor and passed this record in 2012). But it also was a soap from the radio heyday, having launched in January 1937. That ended a nearly-73-year old scripted production. So how did GL fall? A ratings hit well into the 90's, it hit a sharp decline during the Seinfeld era. Save for a brief late-90's renaissance, it frequently placed in the bottom of the Nielsens pack. Cruise through Wikipedia's article on the series, readers will notice frequent changes in writers and producers. Perhaps TVRG's commenting muse Smoo will shine some light on the workings of what went wrong. Then, starting in early 2008, the New York based production moved to New Jersey to slash the budget by one-third. The quality changed as the soap adopted the Blair Witch-esque steadicam, leaving older viewers dizzy. Countless changes and poor writing sank the show, which was replaced by gameshow Let's Make a Deal.Days of Our Lives nosed up in the ratings as all CBS shows experienced significant declines. ABC soaps held steady, and GL's sister show, As the World Turns, experienced a sharp drop and was speculated as the next rumored casualty.
Having dueled for Nielsens since 1978 for the 3pm timeslot, GH emerged victorious and left the 3pm timeslot bare and vacant.
Source -- https://en.wikipedia.org/wiki/List_of_U.S._daytime_soap_opera_ratings