My answer is the same as many others. Before
I discovered Korean dramas, iwas watching american shows such as ER,Nypd Blue, Dexter, whatever, and enjoying them. But When I got to watch these Korean shows which were finished, and you knew they were finished, i stopped watching them. If I watch american shows now, they tend to be the mini series'.

In american shows people have to be cool, and in my memory of the shows, people didn't smile a lot. Let's take the x files for instance (one of my favourite shows) Mulder often cracked a joke, which would make a joke,but not a snigger out of Scully. So I was delighed to see people actually smiling in Korean dramas.

American dramas can take themselves very seriously. Now it doesn't happpen in every serious Korean drama, but there have been some where the makers were not afraid to use humour.