Hana Yori Dango, and I've watched the korean one first.
I honestly thought I wouldn't like HYD better but it's so much better in many ways...
I tend to compare each scene (because there are so many scenes that are the same) and HYD has definitely the best ones. And I don't want to spoil anything here, but the ending in HYD is much, much better. It's unforgettable, whereas the korean version is just... well... it just is. Nothing special at all. The acting is also better, especially because Geum Jan Di (korean version) was honestly annoying at times... >.<
Both are really funny and all but I think the romance part definitely stands out in the japanese version.