Restaurant Brandenberg
This is an institution in Zug. Once a restaurant for farmers, this place is extremely popular in the summer, when you can drink a beer outside below the trees. During the "Stierenmärt it's full of farmers, a real authentic Swiss experience.
Restaurant Freimann
This restaurant has the rustic charm of a farmer's house out in the green. In the summer it's a pleasure to sit in the beer garden below the trees and drink a beer and eat a "Cordon Bleu". You will get great value for your money. The menu covers the whole range of good Swiss food. The restaurant inside is quite small. On weekends it's recommended to reserve your table, especially if you want to eat inside.
Ristorante Liguria
The restaurant isn't cheap, but with maybe the best view over the Lake of Zug. Has big windows. Fish food.