Mr. Sunshine was the first kdrama that I ever watched and oh boy, did it set a high bar. From the costumes to the music, the production quality is really high. The story is compelling and while the romance(s) are very central to the show, there's enough going on outside of them that you never feel that things are being neglected in favour of romance.

I've watched it through all of the way twice and loved it just as much the second time.

Spoilers beyond this point!
I am not, and will never be, over the ending. I just cried through the last few episodes. Full sobs as pretty much everyone died.