If someone ever asked me where they can eat authentic good korean food? I'd always answer Ganadara! But be prepared to run into a lineup since this restaurant is near a University and close to downtown.
My favorite is their Bulgogi (Beef) Ramyun, amazing spicy ramen! If it's your first time eating korean food, I'd suggest the classic Bibimbap (Rice with seasoned vegetables, sunny side-up egg and usually beef), it's a great way to introduce korean cuisine and also their spices (optional chili pepper paste, I can't handle spicy food but IT'S SO GOOD!).
Not only that but if you're not too hungry, their Kimbap's (Rice rolls) are amazing snack sized bites or you can go with Tteokbokki which are rice cakes and fish cakes dipped in a spicy sauce!
My only downside tothis restaurany is the restricted small area they have and the lineups on weekends (But hey, everyone wants to eat amazing food!)