Both are supernatural horror films. There is a lot of mystery surrounding them and the feeling and presence of unease is there.

Director Jang Jae-hyun's debut film. Both are supernatural horrors, the director specializes in the occult genre.

Highly anticipated reunion of Zhao Liying and Lin Gengxin. Both playing leads once again and as love interests.

A marriage gone cold, with both sides slowly finding love again. Both have rich FL and poor ML. Both contain romantic comedy elements.

One film is based on the coup d'etat carried out by dictator Chun Doo-hwan which puts him in power, while the other captures the Gwangju Uprising and massacre of the protestors one year later, which Chun is notoriously responsible for.

FL longs for a man and mistaken and fell for another man that she thought was the man she's waiting for.

Both starring Andy Lau as low-level gangster. Bad boy with a soft heart.
Story involves him struggling to find balance between his relationship and mafia life.

Reunion between screenwriter Park Ji-eun and Kim Soo-hyun as ML, second romcom featuring both. Queen of Tears is missing fantasy element in My Love from the Star. Rich FL in both.

Both directed by Lee Byeong-heon.
Both starring Ryu Seung-ryong as main character running fried chicken joint.
Both contains mystery and comedy.

Hwang Jung-min masterclass.
Noir crime thrillers.
Corruption.
Cops vs organized crime in New World, Cops vs corrupt mayor in Asura.

I want to make a correction to the below recommendation that Chicago Typewriter is NOT set during the Joseon period, but during Korea under Japanese rule, while Mr. Sunshine is set right before that, during the brief awkward period between Joseon and Japanese rule (called the Korean Empire 1897-1910).

Prequel and sequel, and both starring Hu Ge as the main lead. Both are considered classics in chinese dramas.