There is no 'golden age of Christmas'. Christmas is an ancient religious as well as a secular festival. Part of it is religious, and part of it is secular. Going to church is the religious part, eat and be merry plus the gifts is the secular part. Christmas is somewhat differently celebrated in different countries. And it is celebrated somewhat differently over time.
In America and England Christmas Day itself is one official holiday. The next day is called Boxing Day. That day is not exactly the same as Christmas Day. In my country, The Netherlands, we call it Eerste Kerstdag and Tweede Kerstdag (First and Second Christmas Day, literally). Both days are official holidays.
In some countries giving gifts is an important part of Christmas, in others it is not. In The Netherlands, for example, giving gifts is a recent addition to the tradition. Gifts are more commonly given there on 5 Dec, on Saint Nicholas Eve. Father Christmas derives from Saint Nicholas. And his name Kris Kringle is probably from the German word Christkindl.
As I said, it is celebrated somewhat differently in different countries. What you are asking is the current Anglo Saxon tradition, which sort of emerged in Victorian times. It emerged out of much older traditions, and it merges into what it is today. It won't stop there, it will always change according to the times.
If you want to know when the golden age of Christmas was: right now. Nowhere in history have more people celebrated and in such luxurious ways Christmas. I recall vividly we had 1 egg for Christmas breakfast extra (normally we didn't get any, or on special Sundays only) and a large chicken for dinner. Forget getting X-boxes in' your stocking. A small present was all you got. For 'a small present' read 'one'.
I happen to live in Thailand were Christmas is not a tradition at all. Christmas is, after all, a Christian festival. Thailand is a Buddhist country. Christmas Day is just another day like any other. But you do see lots of Christmas decorations in usually upscale shops and restaurants. Mainly for the businesses, and Thais like parties a lot. We celebrate New Year 3 times: Western (December), Chinese (February) and Thai (April), for example.
Complaints that the festival is too secular are as old as Christmas itself.
As to your question about the 'golden location': any particular reason at all to assume London or New York? The Christmas story, if I recall correctly, plays somewhere in the Middle East. The world is bigger than just the English speaking world, you know.