It used to look so weird and fake to me, now I can't stop watching! Empress Ki, Moon Lovers, Six Flying Dragons are all so good!!! Does anyone have more suggestions?

The same story for me. Since I watched the beginning from Goblin, I tried to watch a full historical drama and movie, and I like it now. I don't have any suggestions since I just started to watching it, but I keep this in my mind when I have something.
You have to watch Dae Jang Geum (Jewel in the Palace). That was the drama that partly made South Korea famous. I just watched it a few months ago, and it became my most favorite historical drama.  I also liked Hong Gil Dong even though it is on the sillier side. Chuno and Moon that Embraces the Sun was pretty good too. I watched Queen Seon Deok but I didn't really like it but maybe you might like it since you liked Empress Ki (fyi I wasn't able to finish six flying dragons either lol). I also tried watching Dong Yi but I stopped about halfway..it was a bit repititive lol.
Because you have seen the light, my friend lol. xD I'm sure everyone will recommend a bunch of historical dramas soon enough and most will repeat, so I'll just throw one at you for now: Iljimae
The Princess' Man
Maids
Shine or Go Crazy
Since you like Six Flying Dragon, I'd recommend Queen Seondeok, A Tree with Deep Roots, and Jewel in the Palace--all of them were penned by the person. I'd also recommend the vastly underappreciated Jejoongwon, if you're interested in watching late Joseon/early Japanese colonial-era physicians in action. And if you're looking for something lighter, Sungkyunkwan Scandal, featuring gender bender shenanigans and broody Yoo Ah-in (Yi Bang-won in SFD) as a second (?) male lead.
Jackpot/The Royal Gambler

Iljimae

Arang and the Magistrate

currently airing:  Rebel: The Thief Who Stole The People - it's really really good
For me was the same, I start to like them after watching Faith
Me too.. I really don't want to watch historical because I thought it was boring and because it has sooo many episodes but after I watch Ja Myung Go, well because of Jung Kyung Ho last year and now Im looking forward to see all!!And I can't stop!! I already watched Empress Ki, Queen Seon Duk,Chuno, Tree with Deep Roots, Princess Man, 1/8 of Six flying dragons. But my favorite was Queen Seon Duk.. Because Bidam is love.. :) But also story is good.. :)

I definitely recommeded all the historical drama.. I will start Jumong when Im not busy ...:)
The Princess Man'
Iljimae
Warrior Baek Dong Soo
Queen Seon Duk
It was the same for me but it's one of my favourite genres. Let me repeat Warrior Baek Dong Soo, The Royal Gambler, Rebel.
plus Splash Splash LOVE- not a 'real' historical drama but still enjoyable and sweet.
Love in the Moonlight/Moonlight Drawn by Clouds!
Highly Recommended:

Moon Embracing the Sun
Mirror of the Witch
Jumong
Jewel in the palace
The Horse Doctor
It's never too late to fall in love with sageuks LOL They're amazing!

I Recommend;

[1] The Princess' Man -
[ This was my first ever historical drama that i watched and i'm always happy to recommend this to anyone and everyone. It's like the Korean Version of Romeo and Juliet, with Amazing Chemistry, Forbidden Love, Revenge and the perfect balance of politics that won't bore you! ]
[2] Dong Yi
[3] Splash Splash Love
[4] Jumong
[5] The Legend