You don't say which part of Center City you will stay, but since I live in the Rittenhouse Square area, I will list a few of my favorite restaurants in this part of the city. This list does not include any large steak or seafood houses or any of the super high-end places. Most of these are smaller, more casual restaurants. If you are interested in ethnic food, I can tell you which are the good places in Chinatown. I don't know anything about the Indian places.
In my neighborhood (Rittenhouse Square):
Twenty Manning http://www.twentymanning.com/
Very popular, stylish bistro, frequented by people who live in the neighborhood. Has a nice $33.00 fixed price menu (appetizer, entre, desert). This is where I usually take out of towners.
Parc - a brand new French bistro on Rittenhouse Square at 18th and Locust. The new hot spot on the square. Always crowded. Has a very authentic French feel and the prices are reasonable. Lots of sidewalk seating.
The Continental Mid-town – at 18th and Chestnut.
http://www.continentalmidtown.com/
Another popular hip restaurant. Unique, retro menu.
Monks – at 16th and Spruce.
http://www.monkscafe.com/
Very popular Belgian restaurant. Huge selection of Belgian beers and excellent mussels. Always crowded, doesn’t take reservations, but highly recommended.
La Viola- across the street from Monks on 16th street.
http://www.philadelphiarestaurants.c...nt/936/LaViola
Excellent and inexpensive BYOB Italian restaurant.
In other areas of Center City:
Buddakan -
http://www.buddakan.com/
Huge Asian fusion restaurant. Unique, hip atmosphere, excellent food (there is also a location in NYC).
Fork – 306 Market St.
http://www.forkrestaurant.com/
Critically acclaimed restaurant in Old City.
Mixto- near 12th and Pine
http://www.mixtophilly.com/
Caribbean/Cuban food.