I think the 1950s really lasted until 1963 -- up until President Kennedy's assisnation and the Beatles' emergence (oh my, did I just rip off Dream Academy's "Life in a Northern Town?). So after the new American honeymoon of the 1950s ended, what did the 1960s bring besides more, rapid cultural changes? I think the Sixties might have been the best time to be a kid.
By kid, I don't mean a teenager, but rather, a tween and younger. This might be my most controversial decade selection. I'm sure many decades can lay claim to this. Being a kid in the 1950s might have been just as much fun as it was in the 1960s, and anyone whose childhood was in a certain decade might say their decade was the best for kids and provide good arguments.
Here's my argument for the 1960s (and by the way, I'm picking this over my own decade kid decade, the 1970s): Just as American culture aimed itself toward teens in the 1950s, it aimed younger in the next decade. For the first time, things were marketed toward children. Television and movies were created for children. Recreational opportunities were geared toward kids. The whole driving vacation idea was an effort to provide maximum fun for kids.
Of course, the argument exists that marketing anything toward kids is bad, and I don't completely disagree with that. But with that marketing came a ideal that kids were important. The 1960s produced "The Brady Bunch," the Easy-Bake Oven, the "Big Wheel" and "Mary Poppins" -- all with kids in mind.
Maybe more significantly, the Sixties were the last that provided kids this importance without any cynicism or despair, perhaps for the last time. Kids of this decade weren't immune to the turmoil of the world around them -- indeed a 9-year-old boy in 1961 likely ended up fighting in Vietnam -- but they hadn't grown to simply expect it. I think by 1970s, that innocence was lost, for better or for worse.
One other thing about the 1960s -- a kid at this time grew up with the Beatles. Yes, rock 'n' roll was geared toward teens and the slightly older crowd, but much of it trickled down to tweens, and the Beatles were no exception. I imagine it was a thrill to hear a new Beatles song on the radio for a typical 11-year-old in the mid '60s.