Goblin was the first k-drama I saw. Until that moment I had just only watched Japanese dramas, but at the time I already knew Gong Yoo for "Train a Busan" and I had heard so much about the show that I gave it a try.
After this, I watched lots of k-dramas, so I guess this show is to blame that now I'm a k-drama addict. And even having watching so many of them, anything could be compared to Goblin. Without any doubt it's the best drama I've ever seen in my entire life.
Everything is wonderful. The story (from a non-used to k-dramas point of view) is kind of unusual. The photography, the settings (oh, Quebec, one of the most wonderful places I've ever been), the dialogues, the humor, the bromance, the romance...
I love Gong Yoo in every one of the things he has done, but here he is amazing as the lonely tokebi. For the rest of the casting, they are all perfect, overall Lee Dong Wook as the Grim Reaper (his bromance with the Goblin is mythic, so funny!)
Other thing that I really liked in this show is that you don't have a love triangle, nor the tropes so used in other dramas, and you have the opportunity to see the evolution in both couples.
The only thing I complain is that the main couple does not have much explanation time at the ending  as they should have. There were too much time to explain the Grim Reapers and Sunny (not Sun Hee) future and not so much for the main couple... Dommage!
This show taugh me so many things I could continue for hours explaining why everybody should watch it.
I have read some bad reviews explaining that it's so slow that is boring. I don't know but for me it wasn't slow at all. It had the right pace for a perfect development of the story and the characters.
Music: loved it. One of by k-drama OST.
Rewatch value: I've watched this show three times already and I watch it every now and then while I deciding what to see next.
So, last advise, DON'T MISS IT, BEST DRAMA EVER!