There is no better way to learn about the cuisine of a neighborhood than to get the perspective of a local. Helena Seo has lived and patronized Korean restaurants in Sunnyvale since 2002 and generously shared her perspective.
I lived in Sunnyvale from 2002-2008 before moving up the Peninsula. But, I missed the restaurants in Sunnyvale and eventually moved back to be closer. I’ve tried almost all the Korean restaurants in the area. I usually rely on word of mouth from my Korean friends, but also check out Yelp reviews from other Koreans as a guide.
I’ve personally known the owner of SDG Tofu House since 2002 when I just got married. He still greets me to this day as “newlywed” everytime I come in with my husband or friend or colleagues. The location in Sunnyvale is his first location and he has since expanded to multiple locations in the Bay Area.
So, from my personal experience, I can recommend the following as my favorites:
Great variety of Korean food in quality, good service and amazing side dishes (unlimited refill!). There are tables with Korean barbeque grills as well. It's group friendly!