We just returned from a week in Yellowstone/Grand Teton. Lots of options for eating:

In YNP park: Cafeterias at Lake and Canyon are reasonable, food is
ok.
Roosevelt Lodge has old fashioned "western style"
cooking–ribs and "Rosie beans" are great–reasonable
prices.
Yellowstone General Stores (formerly Ham Stores) have
grills and Wilcoxins ice cream (can’t be beatr!).
Old Faithful Inn and Lake Hotel have more formal dining
rooms–but the atmosphere is better than the food–also
slightly more pricey.

West Yellowstone: Pete’s Pasta and Pizza–self explanatory menu, good
food, reasonable prices.
Running Bear Pancake House–family owned, good food
reasonable prices–worth the normal wait.
Bullwinkle’s–a Green Bay Packers themed bar–mixed
menu, varied prices–most food good
Arrowleaf Ice Cream–not as good as Wilcoxins, but
better than most

Gardiner: Helens– burgers, both traditional and buffalo–drive-in
type restaurant, but reasonable and good
Outlaws Pizza–food and price good, but the service is
awful (hopefully it will improve as the summer progresses)
Park Street Grill–more upscale, but excellent food,
slightly pricey

Cooke City/Silvergate: Log Cabin Cafe—excellent breakfast, all else
good–try the trout–good prices
Grizzly Pad–also excellent breakfasts, plus
burger/fry/shake specials-family owned ans
reasonable
Beartooth Cafe–lunch/dinner–varied menu–try
black bean nachos and garlic burgers–good
prices
Buns and Beds Deli–deli type sandwiches and
specials

Cody–Irma Hotel for prime rib
The Noon Break for breakfast/lunch (check Roadfood book for this
one)
Don’t miss the Buffalo Bill Museum–the best Western History and
Art Museum in the country!

Actually, most of the "out of park" restaurants are family owned–except for Outlaws and the Irma. Owners are usually around, which, in my opinion, keeps things on the up and up.

If you’re headed to the Tetons, I have a pretty good list for there, too. Just let me know!