So I need a new drama and this is my list of prospects : Lie to Me , D-Day , I Remember You, Answer Me 1988. I want a drama that features a prominent happy ending romance. It does not have to be a romance drama but have plenty of romance. Kind of like Cheer Up! and Healer.
Lie To Me, def. The main couple had tons of chemistry and their kiss scenes were the best!
Answer Me 1988 is really really good tho and I def rec that too.
Okay , thanks so much!
Lie to me .... the pairing seems a bit 'off' at the beginning but as you keep watching you totally ship them.

I remember you is also good but the romance is def better in LTM
Oh, thanks! So nobody said anything about Answer Me 1988... so I guess it has no romantic plot? 
D-Day is an amazing drama, but the romance isn't heavily focused on. It's there, but if you want to watch something specifically for the romance I'd wait and watch this one later. (But don't pass it up, it's really good.)
D-Day ,  and I Remember You, both are great dramas, and the romances in both are cute :)
Reply 1988 is fantastic (or well.. from what i have seen so far) but it is less oriented around romance and more around family and friendship (romance IS there though) Reply 1997 has more romance than 1988 and it is also shorter, i think you should try at least one of reply series :))

I remember you is great as well but again not focused on romance like.. at all? The romance is there but the show focuses on different things

Lie to me has romance from the begining but in the end it got kinda repetitive. I had fun watching it, however it is bit worse than Reply or I remember you
If you want romance Lie to Me is your best bet. As far as I know neither I Remember You or D-Day are high on romance. Out of the ones you listed Answer me 1988 is the best but it focuses more on family and friendship then it does on love. 
'I remember you' is a very good drama, but falls short in the romance department. You can feel their affection and there are some really nice moments, but not many definite 'OMG' scenes lol
Reply 1988 is the best 
I think Lie to Me is the one with the most prominent happy ending