Idol actors are usually overrated. I used to think Park Shin Hye was overrated but I think she has become better.
Lee Min Ho and Song Joong Ki are only popular because people find them good looking, their acting are ok but not equivalent to their popularity. I dont get the thing with Jang Geun Suk at all, can't stand him..
Even tho I kind of like Lee Jong Suk myself I do think he is a bit overrated, so far he has only been albe to pull of one kind of role. It's about time that he proves his abilities by accepting a role that might be a little bit of a challange to him.
I think Jang Na Ra is a good actress but I don't really like her acting style so I usually don't enjoy her dramas.
Also, Suzy. LMH until recently. I can't hate him even though he's not a great actor. He's LMH :3. IU - went from "oh so cute" to "gah, she's annoying" to "she's pretty" after having seen Scarlet Heart: Ryeo. She's on the okay list for now. Park Shin Hye wiggled her way into "okay, you're not bad" after Doctors. Bo Gum - Annoyed by the stills from his recent historical Love in the Moonlight.
I love Park Shin Hye, but I understand why some people think she's overrated. She's not a groundbreaking actress, but there's something really refreshing about her for me.
I second idol actors, Song Hye Kyo, and Hwang Jung Eum though. It's always disappointing seeing a new drama filled with idol actors (with a few exceptions like Eunji and Sungjae). Song Hye Kyo is a bit bland for me and like Aceji said, Hwang Jung Eum just screams all the time.
Unpopular opinion but I never cared for Gong Hyo Jin.
I hate Lee Min Ho. Part of it is because he always plays the arrogant rich boy. Kdramas are filled with them but while some actors such as Kim Woo Bin and Gong Yoo can be arrogant and likeable Lee Min Ho remains just arrogant. Another reason for my dislike is because his acting consists of tipping his head down, tapping his nose/forehead while sighing, then throwing his head back and exclaiming "ahhh."
Gu Hye Seon, Lee Seung Gi are also on my overrated list but to a lesser extent.
I generally am not that critical when it come to actors - I don't know why, I guess I just don't really realize that they are bad? But then again, there are some actors who make me question of I want to watch a drama at all - I don't think that's really 'overrated' but anyways.
I agree with what others have said - a lot of the time idols get more credit than I think they deserve.. on the top of my head I can just think of Seohyun from SNSD and some of the boys from Infinite (which I love). To be honest I also think T.O.P gets a bit more credit than he is due.. Other than that, Hwang Jung Eum kinda irritates me (even though I managed to really enjoy She was Pretty)... It just feels like she over-acts and her voice is a bit irritating. But then again - it might more have been the characters I have seen her in than HER.