Muhani:
From your list, I'd recommend:
King2Hearts is just generally amazing and a must-watch
Can You Hear My Heart is a bit on the longer side (for me, anyways), but it's really sweet and well-done; the music is also lovely and the characters/acting are absolutely wonderful
Nice Guy/The Innocent Man- I adore this drama. I never watch melos, yet I still adore this drama. It's still airing (I think it has 16 episodes out at the moment, or something like that?) but so far, it's been a fantastic, well-written, amazingly-acted drama. Song Joong Ki and Moon Chae Won are a gorgeous couple, and they are both exceptional actors and exceptional in these roles. The story is very well plotted, and well executed as well; there are unbelievable plot twists and heartwrenching moments every episode.
For whomever does my recommendation:
Could you please perhaps recommend some lesser known dramas? (I.e. I know City Hunter and Gaksital, etc, are supposed to be amazing, and I will watch them when I have time, and so I want to know about other dramas that I might not otherwise get around to.