The original texts were very 19th century. I recall an incident in one of them where Dr Watson, while he is still married, goes to visit Holmes, to find Holmes has used his revolver to shoot holes in the wall in the shape of a letter V as an indication of his patriotic loyality to his Queen.
Like all good psuedo science fiction, the stories stem just past the bounds of reality. The modern term I believe is cromulence. This seems to be a feature of almost all modern drama and most modern examples of crime drama.
The contemporary element was the portrayal of 19th century, English, high values. It is the adaptability of the characters into different eras which make the creations so successful.
I watched the second half of a episode of Sherlock a few nights ago, largely because of this thread. It was very Dr Who. in its production and direction. The psuedo science has managed to remain just the other side of preposterus. But the thinking process of the main character was, well, bit OTT.