As the New York Times reported back in 2007: "By 1958-59, 8 of the Top 10 shows were westerns; a year later there were 48 westerns on television, including 30 in prime time."
I definitely have fond memories as kid of watching a wide variety of Western TV shows (and movies too, broadcast on TV), not to mention much else that was countrified ("Hee Haw" and "Green Acres," etc.)... but that really all went up in (gun)smoke by the early 70s.
At this point in my life--I was seven--I didn't watch a whole lot that wasn't westerns. Sure, some kiddie shows most Americans haven't heard of, and maybe I LOVE LUCY and I MARRIED JOAN, but for the most part, horses and six guns all the way. ROY ROGERS, THE CISCO KID, THE LONE RANGER, HOPALONG CASSIDY, and an occasional GUNSMOKE (GUNLAW in England).
"Leave It To Beaver" wasn't a ratings winner when it originally aired. In fact, it was nearly canceled, a couple of seasons in, or so (I don't remember which season), and switched networks. It became bigger in syndicated reruns.