I have two favorites, I've been to a handful of places. Hankook on Collier Rd. is Korean-Mexican fusion and it's awesome. I go there at least once a week.
My Korean friend takes me to Hae Woon Dae on Buford Hwy just outside the perimeter. It's his favorite traditional sit-down type restaurant. We've each tried other places and that place is so far the best one we've each been to.
For BBQ he recommends Iron Age on Pleasant Hill. All you can eat for $25. I've not tried it yet but I trust his taste.