Some that really come to my mind would be:
Chicago Typewriter - this drama has almost everything, from the story to the acting talent and the cinematography. It gave me all the feels and I've watched a LOT of dramas in my life so I can say I am a bit picky. The leads have great chemistry and their story is very meaningful and touched by destiny if may say so.
Coffee Prince - this one is a classic and I think anyone will tell you that. It's sweet, it sizzles of the charts with the 2 main leads and it sometimes gets hot and steamy. Really well structured and great chemistry, I still remember it after watching it so many years ago!
Descendants of the Sun - this can seem as a safe answer but I really don't care. As hyped as this drama was, in my opinion it deserved it because it was freaking great. The main couple accept their feelings pretty early and work together for the relationship to work. They also go through different events in their life which solidify their love for each other + the secondary couple is as good as the first so you buy 2 at the price of one!
Goblin - another one where you get 2 marvelous love stories in one drama, fate also plays a big part in all of this and it makes their interaction so much more meaningful!
Goong - this one is another drama that I consider one of my little jewels. Another classic if you were to ask me with a compelling love story. The girl falls for the guy first and he is a little hardheaded but oh well, you go on with the ride. Their chemistry is amazing and it's one of the few dramas I have rewatched a couple of times because of the main leads.
MARS - this one would be my favorite drama of all time. When I think bout epic love stories then this is where my mind goes to. Everything is so beautiful and emotional from the beginning to the end and their relationship grows stronger with every episode. A must watch in my books!
Tatta Hitotsu no Koi - another one that I've rewatched a couple of times. One of the most well done romance drama out there. It sucks you in from the beginning and never lets you out even when you have finished it. I think this one would be the perfect fit for what you are looking for.
The Princess' Man - one of my favorite historic romantic drama out there. Everything is beautifully done, it has action, romance and it sometimes keeps you on your toes. These 2 main leads and amazing to watch together and you can't get enough of them, all the feels are there trust me.
I could really add more but I think I will leave you with the ones that had the most impact on me and are also really memorable even years after. Hope you will find something interesting in here. Also, I wrote an article a few years back exactly on this theme so maybe you would like to take a look upon that as well: Neverending Stories (keep in mind that this was written in 2013, so a lot of dramas appeared since then)
