I moved here 14 years ago from a populous area and love it. Millions of people come here for vacations because of Mt. Rushmore, the Sturgis Motorcycle Rally, Crazy Horse, or come through here to hit the Rockies.
But if you don't know where to go for food, you can wind up with some fairly lousy fare from proprietors who serve microwaved distributor food.
So here's some tips for good eating:
The Alpine Inn, Hill City, the heart of the hills--a German-inspired lunch menu in a beautifully restored historic hotel. Night time menu features only a steak dinner with potato and salad, but it's good and wallet-friendly. Accepts only checks and cash though.
Enigma, Rapid City--all organic menu, fantastic salads, steaks and specialties. Not exactly family-friendly but perfect for couples.
Their "Fork and Knife Caesar" is the best I've ever had.
Custer (southern hills)--Sage Creek Grille. Open-faced salmon salad/sandwich is divine
Spearfish (northern hills) The Bay Leaf Cafe--uses locally-sourced foods. Wonderful charming, simple atmosphere.
As a general rule of thumb, when you're in the tourist-trap towns (Deadwood, Wall, Sturgis), the food is fairly dismal, so it's best to drive to Hill City, Custer, Spearfish or Rapid City to eat.
You can always Yelp these if you're dubious, and no, I don't own, nor have friends who own, any of these places. I'm just sharing the foodie-joy.
Enjoy and happy vacationing!