My first drama was actually the Taiwanese version of Hana Kimi which I fell in love with! When I moved onto Korean dramas I discovered a whole new world of awesome... My first Korean drama that really had me hooked for the rest of forever was You're Beautiful haha.
My first KOREAN drama was either Playful Kiss or My Princess. Can't remember which one :'''D
For me it's Autumn in my heart.
mine were Boys over flowers and City Hunter and after that the rest is history :D :D :D
Mine was Full House. 
Can you hear my heart! 
I think it was Boys Over Flowers ahaha, though I've watched so many amazing dramas since then <3
idk if I already responded to this, but mine was Hana Kimi... I believe it was the Taiwanese version. But after watching all the other versions I didn't really care to watch anything else until my friend got me to watch Sungkyunkwan Scandal. After that I started looking for more good dramas. 
Short answer: KPOP Extreme Survival on Netflix (I am so embarrassed.)

Long answer: I am a long term/huge fan of Survivor (US version) to the point where I listen to podcasts about it. One of my favorite podcasts began reviewing the Korean game show The Genius which then led me to Netflix to watch more Korean shows. My first KDrama was  KPOP Extreme Survival (singing, Baby, say yes!). Then Boys Over Flowers, You're Beautiful and a premium subscription to Dramafever makes me side eye my cable payment each month.  
Mimi or Paradise Ranch, I don't remember XD