A lot of it depends on what cuisine and how much money you want to spend.
For example, on 44th Street in midtown, there are a number of restaurants that participate in a prix fix menu on Wednesdays that keeps the prices reasonable. You can literally get any cuisine that you want.
There are a couple of good French places off of 51st and 8th Avenue - Tou va Bien and Rene Pujol - good food, prices not completely out of control. There are the typical big steakhouses throughout - Gallaghers, Smith and Wollensky, etc.
Depending on how formal you want, if you like barbecue, Virgil's is great - it's on 44th street off of Broadway.
You can find a good restaurant all over the place there.