Moon Lovers: Scarlet Heart Ryeo (2016)

Synopsis of Scarlet Heart:
When a total eclipse of the sun takes place, Go Ha Jin is transported back in time to the start of the Goryeo Dynasty of Korea during King Taejo's rule. She wakes up in the body of the 16-year-old Hae Soo and finds herself living in the house of the 8th Prince Wang Wook, who is married to Hae Soo's cousin. She soon befriends several of the princes and meets the ostracized 4th Prince, Wang So. Although knowing she should not get involved in palace intrigues over the succession to the throne, she inadvertently becomes a pawn in the struggle, as several of the Princes fall in love with her.

Scarlet heart and Bloody heart is both historical drama that is also a romance drama. Both main lead becomes the king.

The main actress is also in Scarlet heart too!

Both are about a modern day FL who travels into the past and finds herself in a love triangle involving at least one prince.

After an accident, the soul of a 21 century woman traveling back into another time/paralele universe into the body of a dying woman. But is the Korean version of the c-drama "Scarlet Heart". Like "Palace" (Gong) It is a melodrama.

Both are about a person time traveling to a very different era - one is past to future, the other future to past.

There is similarity betweeen princes in ML and three friends in GF, characters was changing from harmonious friends to enemies in both shows.

Not too similar except the fact that Lee Joon Gi is the lead in both dramas and the romance of his character and the female lead are crucial in both dramas.
However, I am recommending Flower of Evil to Moon Lovers fans because Flower of Evil is such an underrated drama and more people need to watch it. I know Lee Joon Gi has many fans from Moon Lovers, so I hope his Moon Lovers fans can watch Flower of Evil. Don't undersestimate the female lead, Moon Chae Won may not be the most popular to today's kdrama audiences but she is an acclaimed actress and she has great chemistry with Lee Joon Gi.
As for Flower of Evil fans, it is good to recommend Moon Lovers since it is indeed one of Lee Joon Gi's most popular roles, it's a good idea to watch it for Flower of Evil fans to understand why Moon Lovers fans hype Lee Joon Gi's role in this show so much. And Lee Joon Gi did a great job in this role too.

Both are about a modern day FL who travels into the past and finds herself in involved with at least one prince.

Both female lead were favor, but has sad ending.
Both female lead were kind, beautiful
Both young ming were down jealous, no confidence, palace politic

Both are about a modern day FL who travels into the past and finds herself unexpectently falling in love.

The beautiful female lead and the young king were deeply in love.
Due to stupid young king and palace conspiracy, dirty politician, they were apart
Can’t get my eyes off the queen
Beautiful historical drama

Both are about a modern day FL who travels into the past into the body and identity of another girl.

Both were historical drama.
Both female leads were beautiful.
The main lead were deeply in love
However, ending were sad

I recommend this both drama because , Male lead and Female lead
try to solve problem
In one drama explosion and another student murder/suicide

When a total eclipse of the sun takes place, Go Ha Jin is transported back in time to the start of the Goryeo Dynasty of Korea during King Taejo's rule. She wakes up in the body of the 16-year-old Hae Soo and finds herself living in the house of the 8th Prince Wang Wook, who is married to Hae Soo's cousin. She soon befriends several of the princes and meets the ostracized 4th Prince, Wang So. Although knowing she should not get involved in palace intrigues over the succession to the throne, she inadvertently becomes a pawn in the struggle, as several of the Princes fall in love with her.

Both are about a modern day FL who travels into the past and finds herself in involved with at least one prince. Both have the same sad ending.