So far my favorites and best ones I seen are old but this are the ones I still re-watch, make me cried and laugh. All have really happy endings too.
Life Is Beautiful 2010 - is just beautiful.
Family's Honor 2008 - didn't care for the main OTP, but loved the all secondary couples and I loved the all main family, such a beautiful and moving story, one of the best, great ending too.
Pure 19 - 2006 daily drama, funny, cute main OTP, loved the music and loved all the characters, specially the male lead's family. Is 167 episodes but the sub version is edited into 122 of 40 min or so instead of the normal 20-30min version, so it didn't felt that long for me, the longest drama I seen was 173.
Golden Bride 2007 - arranged marriage between a half Korean/half Vietnamese girl and Korean guy who is suffering from emotional/mental problems after an incident with his ex, the girl helps him through it and he tries to help her find her Korean dad who left her when she was a baby. The most skinship/kissing i seen between an OTP in family drama so far and I really liked the way the family cared for the female lead specially the mother in law.
Golden Era of Daughters in Law and I Believe in Love - same writer
GEOTIL - really funny, only cared for the second OTP story though, but still find it pretty good as a whole, I specially loved the last few episodes and the songs.
IBIL - didn't like the older son's story but loved the adopted daughter and the family's older cousin story the most starting in episode 4-5, some characters I find really annoying but ended liking them except one, really good ending too.