Master's sun, Descendants of the sun, Goblin,KMHM, Defendant, Chicago Typewriter, You who came from the stars,Splash splash love, Strong woman do bong soon,Moon Lovers, White Christmas( it was fine but i expected way too much i guess from hearing all the endless praise), The moon that embraces the sun... 
The Heirs (This the THE WORST for me, just horrible)
Playful Kiss (hate it, annoying message of submission, annoying romance)
Strong woman do bong soon (funny but just that)
Goblin (no comments)
W- two worlds (promising but meh)
Legend of the blue sea (female character = lost puppy, no story)
Bromance (too bad)
Doctors (meh)
My fair lady- 2009 (pretty average)
She was pretty (meh x2)

the k2, you who came from star, boys over flowers, DOTS
The Master's Sun 
City Hunter
You Who Came From the Stars
Goblin

W

The last two, I get the pre-release hype (I was really excited about them too), but the actual product fell short of expectations. 

About Legend of the Blue Sea, I personally felt the hype was well correlated. Like, when it was good, the hype was good, but when the plot made a left turn, people noticed and criticized it right away (at least on MDL). 
Boys over Flowers
W
The Heirs
Voice
You Who Came from the Stars
Any version of Itazura na Kiss (i really don't get why it's so popular)
Dramas where I understand WHY it is hyped, but I DO feel like there's enough of a counter voice that frequently points out the terribleness of them: 

Boys over Flowers
The Heirs


Dramas where I understand WHY it is hyped, but I DON'T feel like there's enough of a counter voice that frequently points out the terribleness of them: 

Faith
Descendants of the Sun
Love in the Moonlight
Oh My Venus
Secret Garden
Weightlifting Fairy, Kim Bok Joo
I Remember You
Arang and the Magistrate

Dramas where I DON'T understand why it is hyped and I DON'T feel like there's enough of a counter voice that frequently points out the terribleness of them:

Chief Kim
King of Baking, Kim Tak Goo
Innocent Man
A Gentleman's Dignity
Secret Garden
Coffee Prince
Boys Over Flowers
Most of them were named already, but Descendants of the Sun, Yong Pal and Doctors dropped them all too
Secret Garden
Goblin
My Girlfriend is a Gumiho
The Moon That Embraces the Sun 

*Spoilers*

Secret Garden is a show I wish never existed. It's got a pretty cool concept but it's one of the most disrespectful shows I've ever seen. The main guy doesn't care about his romantic interest's opinions or wants. He just wants what he wants and he expects her to give it to him regardless of whether or not she wants to be involved. Sometimes he backs off, but it's after she tells him "no" several times. Sometimes he just straight up ignores her protests. He is irrefutably abusive. 

Goblin is a show that i think would have been better if there were less episodes. With so much extra time, we instead get long pans of people looking into nothing. Some call it "artsy," I call it repetitive and a waste of time. Instead, it'd be nice to develop the story more. It also kept coming back to the same plot points over and over again (his back and forth decision over whether or not he should tell her the truth/whether or not he should let himself die). I think a shorter series could have made this show feel smoother and get to the meat of it faster. 

I don't really remember the other two, but I dropped them despite having heard they were amazing. I think I just thought The Moon That Embraces the Sun was just too ridiculous. I don't remember what my problem was with My Girlfriend is a Gumiho.
Another drama I just thought of is Empress Ki...I'm a die hard romance fan,and I heard the romance was everything...I tried to watch it,but I gave up before episode 10....
SPOILERS
When the drama first came on,the main leads were getting married...She was longing for the second lead...Then they took you back to the beginning when the female lead first met the male leads...Then I read some spoilers that said the entire drama is based on flashbacks,and after she became queen-.- I'm not a fan of flashbacks,I'd rather a few flashbacks and watch them in the present day.....I just didn't get all the hype for it
Definitely boys over flowers, I've never understood why people like it.
Arang and the Magistrate & Goong
You who came from the stars
Healer
Goblin