Good restaurant is very objective. Having a price range and favorite type of food might help.
As others have said, airport is about 15 minutes from any civilization -- near I-70/Pena (Pena is road from airport to I-70), there is an Applebee's and a few other standard restaurants.
There's a Carabba's not too far from there - about 20 minutes. Iliff/225
It's about 30 minutes to downtown Denver, and then your choices are quite open.
Stapleton area is also about 20 minutes from airport. List of places to eat there:
http://www.stapletondenver.com/Shop-Nosh-Stroll-Where-to-Eat.aspx