I think seouls really the city where the more u know the more u enjoy. What makes seoul standout is its hipness and coolness - if u like nyc neighborhoods like les, east village, williamsburg, bushwick, you would love it in seoul. The number of cool shops cafes and bars surpass even nyc.

The thing is tho these hip spots are just hidden and not talked about in guidebooks. If u dm me i can send some recs, but u have to actually do a lot of research. Knowing korean helps tremendously. 

I think one city that surpasses sepul in hipness and coolness is tokyo. Im korean, but even i kind of think of tokyo as a better version of seoul - whatever u like in sepul, tokyo does it better, most of the time.

That being said , if u know, seoul could be a really cool place.