It's Time travel, funny leads and good chemistry between the casts. So, I think this is the best choice for those who likes watching time travel dramas. And you won't expect things coming in Oh, my emperor.
Same time travel and the most funny drama ever. If you love My Assassin Girlfriend, you also might like oh my emperor too. There is a sad scene but it would be over in 2 episodes as I remember.
Similar vibes and concept. A king traveled to the present. My Assassin Girlfriend seems to focus on less characters so the plot may be easier to follow.
Similar concepts where a king travels to the present. Though the king in My Assassin Girlfriend seems to be more intelligent when it comes to navigating the modern world.