Remember, these episodes were made in the late 70s and early 80s; viewing figures of 20 million was not unusual in the uk. Also, take note, there was no home computers, no Internet, no mobile phones. Try to watch the episodes in a quiet room and get into each character.
Regarding the USA episodes, watch 'Light Fingers'. I think this is one of the best in the box set.
I agree that they lack that certain something. Almost as if the Americans don't quite get it. Saying that, I do enjoy a couple of them. Particularly "Heir Presumptuous" and "Sauce for the Goose" albeit mainly for the endings.