We are performing scheduled database maintenance, which may cause temporary downtime. We appreciate your patience and apologize for any inconvenience.
Revenge (2005) was my first. Still one of my favourites to this day.
Playful Kiss was my first... I transitioned from anime (Ouran High School Host Club) to manga (Itazura Na Kiss) to drama... My second was Boys Over Flowers I believe.
Depends on how far fetched the question is. The first ever asian drama I watched was Skip Beat. And because of this I found other websites with those. So, after that it was Playful Kiss and My Princess. And then I couldn't stop anymore xD
Mine was probably Goong. When I first watched it I knew nothing of korean culture ( save for a few kpop songs...I wasn't a kpop fan back then ) so the palace and plot really intrigued me. I actually didn't finish that drama, I believe the first kdrama I finished was Secret Garden. It's still one of my faves.
It was Autumn's Tale - that was the first time I fell for Song Seung Hoon & Won Bin, and K-Dramas and there was no going back....
Full House (2004) was my first!
ohhhh man. boys over flowers. LEE MIN-HO.
i was like, 3 years late to watching it, it was so popular when i was around thirteen but i never caught on till ages later.
My first korean drama was Full House.. but the one that got me to dive into the place of no return was Goong!
I think my first drama was Liar Game, but Athena: Goddess of War was the one that made me realise that i love kdrama. 
Mine was Hi! School Love on, my friend introduced me to it because of Sungyeol & WooHyun and I got addicted 
Boys Over Flowers, sadly..
first k-drama was boys before flowers. not as good as he original though lol