What is a kdrama, where you probably would buy a CD that contained all the songs from that drama?
I'm not talking about the kdramas that are like "I like this one song, but the rest is meh." (There are some songs from kdramas that I really like, but feel like that song maybe was the only one that I really liked)
For me, many popular kdramas that I watched as a teen come to mind. E.g. Boys Over Flowers and You're Beautiful.
There is also Heartstrings, which, like You're Beautiful, had Yonghwa and Park Shinhye in the cast and there are some songs from that kdrama that I like. I especially like the song "Because I Miss You" by Yonghwa.
I don't know if "Full House Take 2" was that good of a kdrama, but I actually liked the OSTs.
For "My Girlfriend Is a Gumiho", I really like two songs from it. One of them is "Fox Rain" by Lee Sunhee and the other is "Trap" by No Minwoo (who also was in Full House Take 2, but in the Gumiho drama, he was hotter).
I think that I kinda was a SM Entertainment company stan in the past and I kinda liked the kdrama Mimi, which starred Changmin as the protagonist. I think that drama had songs by the project group "SM the Ballad" (when they had the 2014 lineup change) and then also pre-debut Wendy's song "Because I Love You"
One More Happy Ending (which I watched just because of Conan O'Brian's random cameo lol) has good songs in my opinion. The "Loving You" song by the fictional group Angels and that one song by Kyuhyun (well... I was an ELF back then and Kyuhyun was my SuJu bias).
For recent dramas (by recent, I mean the ones from the 2020's) I can currently only think about Let Me Be Your Knight, which had freaking "Beautiful Breakup" by the fictional band LUNA and also some other nice songs. (heck, "Beautiful Breakup" was one of my SOTY back in 2021.)
I would sound biased, if I say that Imitation has a good OST. (because half of ATEEZ starred in that kdrama)
"Diamond" by Sparkling is the best song from Imitation, just kidding.
There is also Miss Panda and Mr. Hedgehog which has a Super Junior-KRY song and two Donghae songs in the OST, and I was a huge ELF back then when I first watched it.
EDIT: Oh, and I want to add that I feel like many historical kdramas have some really great OSTs, but I currently can't think of any kdrama of that genre where I liked more than one song.