Romance in the Rain and Mars hands down. Romance in the Rain is a tad bit old but definitely the best drama I had ever seen once you get over the fact it was made in the 1990s. 
Right now,

Battle of Changsha 
Legend of Concubine Zhen Huan 
Eternal Love ( 3 Lives 3 Worlds 10 Miles of Peach Blossom)
Boss and Me 
Nirvana In fire 
****edit***

NIRVANA IN FIRE-- trust me and trust the rating.. This will be my favorite c-dramas ever!! unique story. awesome cast!
The Disguiser
Battle of changsha
Love me if you dare
The journey of the flower

Started to watch Surgeons and it was really good... :)
Boss and Me. I'm so frustrated at Feng Teng (main dude) half the time but I LOVE IT~ Super happy ending!
Legend of Concubine Zhen Huan
Eternal Love
Ode to Joy
Nirvana in Fire
Surgeons - soooo good. My new fave  
Battle of Changsha - all time fave
Boss-and-Me - fave C-romcom
Legend of Concubine Zhen Huan 
Nirvana in Fire 
Three Kingdoms 
Cuo Dian Yuan Yang 
Eternal Love - soooo swoony romantic
Palace drama : I think palace drama is my fav. genre of C-drama since i've watched a lot of it compare than other genres, I like Dream of the Red Chamber (1987) ('m not sure if it is a palace drama or not), Huan Zhu Ge Ge a.k.a Princess Pearl I & II (1998 & 1999), Ruby Lin's dramas : Schemes of a Beauty (2010), Introduction of the Princess (2011) and Singing All Along (2016). I also like Three Kingdoms (2010), Scarlet Heart (2011), Legend of Concubine Zhen Huan (2012),  Wu Zetian (2014) and Nirvana in Fire (2015) 

Xianxia drama : Ten Miles of Peach Blossoms (2017), xianxia drama is not my cup of tea since most of the time i can't stand the CGI effect and           storylines are not my liking, Ten Miles of Peach Blossoms is an exception.

Wuxia drama : The Heavenly Sword and Dragon Sabre (2002), Swordsman (2013) -- I love Joe Chen's DFBB

Republican era drama : Romance in the Rain (2001), Cruel Romance (2015), The Disguiser (2015), Rookie Agent Rouge (2016)

Modern drama : Loving, Never Forgetting (2014), Ode to Joy (2016)
Which is the best cdrama among the following. Please, help me pick.
Because of you
15 years to wait for migratory birds
My bratty Princess
My Pig Lady
The fox's Summer

(I don't like slow dramas. Also the two main lead should be good actors at least not bad. Not too frustrating ex gf plot.)
Thanks in advance.
@priririn

I've only watched Because of You, My Bratty Princess and My Pig lady tho but I like "Because of you" more. The guy is handome and cute... hehe
As I always said... haha I have lots in my mind

top 3 (I guess) :
Love O2O
Boss and Me
Love Me or Myself
Rama-Rama wrote: As I always said... haha I have lots in my mind
top 3 (I guess) : Love O2O Boss and Me Love Me or Myself
Thanks a lot. I have watched Boss & me and loveO2O (my favs too). I will checkout beacuse of you and love myself.
I don't watch many..for now it only be Eternal Love ^^
For me, it would be 
Candle in the Tomb
The Lost Tomb
Love O2O