The only one I can really unrecommend is My Lovely Girl. I would unrecommend Koizora, but everyone seems to like that one so I think that's just my preference. There's a few good things on your list though. :')
Well, the only thing from your PTW list that I would unrecommend is Ugly Alert. Lots of people loved this drama, but the male lead had a martyr complex that annoyed me to no end. Like nobody on the planet is that selfless -- the whole noble idiocy thing got very old very fast. I also found one of the main characters exceedingly bitchy. Every time she came on the screen (which was sadly often) I wanted to get violent. I will admit, though, that there were a few cute, romantic moments, but still way too juvenile for my tastes (as most k-dramas). It certainly did not make up for the drama's other faults. Overall, I'm not really sure what made this drama so special for so many people, but for me the investment of 133 hrs of my life wasn't worth it. But, I have weird tastes in dramas and I have no idea what you look for in a drama so if you were really looking forward to watching this show, you probably should just go ahead and do whatever you want.
I would unrecommend Mischange. A lot of people in the comments section seemed to like it but there were so many plotholes that I just couldn't get past. The story itself wasn't as interesting as I thought it would be either. I'd rather have that two hours of my life back. 


Mary Stayed Out All Night was terrible in my opinion but it was one of the first dramas I ever saw so I couldn't really tell at the time. 
I only watched it because of Kim Jae Wook but not even him gave me the strength to finish it.
Uff you have sooo much on your PTW... I'm pretty damn sure the adaption of Gantz sucks so much, it can only suck since portraying what happens in the manga well would cost A DAMN LOT of money... the manga is extremely gruesome (and that is why it's supposed to be enjoyable) - so be warned. If you do want to check it out I highly recommend the manga instead because it is the original story. It includes a whole lot of monsters/aliens.. tbh I haven't seen the movie adaption so take what I am saying with a grain of salt (still, I read the entire story of 37 volumes).
If LDK is as bad as the manga then please do not watch it. The guy is an absolute jerk and treats the girl like shit and she's a very typical shoujo girl (being obsessed with him and being nothing without him...). It is also very predictable.
well from what you said above you don't seem to like the typical shoujo line which is "From Five to Nine", the guy is obsessive af and the girl has to deal with it and suddenly it's love, even tho the lead actors, yamapi and ishihara are perf and I love them, I just couldn't get over the feeling of wasting my time with this cliche drama
Your list is full of Japanese dramas and I just watch Kdramas so there are not many dramas that I can say something about. (actually it's just 2 :D)
But I can say, Cruel City should definetly stay there. TBH I would even recommend you to watch it as soon as possible, cause it's great. And I can't say much about Signal because I just started that myself and watched the first 2 episodes. But it seems interesting. So your Kdramas on your PTW list should stay there :D

And I'm sorry for the next person for my long PTW list :(
I just started Cruel City tonight myself!

A lot of your PTW is dramas I haven't seen but out of the ones I know.... if I had to eliminate one personally, I'd pick Coffee Prince. But I know it's a fan favorite and a classic but it just dragged on forever for me so it's worth a watch, at least for a few episodes. So that being said, next to go would be The Heirs. I can't seem to make it through that at all, and reading the reviews, it seems many people are with me.

I do highly recommend: Who Are You School 2015 (very very frustrating ending but fun to watch nonetheless) and You're Beautiful. Love Shuffle was interesting too, though not quite as good as the first two in my opinion.
@Izaya There aren't a whole lot on your PTW that I have actually seen/didn't like.
So the only one I could possibly unrecommend to you is God's Gift-14 Days. I really enjoyed it however I know so many people who disliked it, solely on the ending alone. It will be completely unexpected and you will either understand it like I did or you will rage like my other MDL friends. So take it or leave it. 
According to almost everyone, Blood was a failure in every aspect so I'd unrecommend that one.
According to me, these are boring ones : Mimi, Saikou no Rikon (some enjoyed it, but personally i felt the pace is so slow), Man of Honor, Switch Girl (many deemed hilarious but imo it's just so corny and over-the-top). 

For movie, No tears for the dead : meh...disappointing movie with a weak plot story.
I unrecommend Yamato Nadeshiko Shichi Henge. 

It's very anime-like.If that's what you like, feel free to ignore me. I sort thought it was funny at first but I got bored with it because I found it too over-the-top.

I'd unrecommend Mirai Nikki (haven't watched it but many fans of the manga I've met said it was terrible in comparison) and xxxHolic.
You Who Came From The Stars was a waste of time for me.
There were so many plotholes and unfinished questions in that story that I still get upset just thinking about it.
I guess since the leads were popular no one cared but I wouldn't recommend it.
Your list is suuper long btw. xD

I guess i'd un-recommend Love-On Air, I watched the movie on a whim since it was listed on dramafever. The movie didn't really leave me with anything substance wise and I fell asleep on it, so I had watched it again and I still didn't like it. The main character was a bit whiny, there wasn't much different music from the group despite it being about music and the romance wasn't that great either.