my all time favorites were
- Moon embracing the sun
- Faith
- Jumong (this one is old and long but it's one of the best once you get through the intro part)
- Iljimae (another old drama, but it's gold !)
- Rebel; the thief who stole the people
- Eternal Love ( this is a C-Drama, and more of a fantasy than historical and it may be long but it's worth it , every single episode is good and there's not a dragging moment in this drama)
- Princess Wei young (another Cdrama, if you like a cunning/smart main female then this one is for you)
- Grand Prince (I just recently discovered this drama and it's one of the hidden gems in kdrama)
So far this is all I remember and they all have romance, I'm a sucker for romance in historical dramas :) and most of these dramas have those "get-through-all-hardships-together kind of love
If you've watched all of them I can recommend more :D Have fun watching