I like Khan's Fire. They do some pretty good stir fry dishes and it's fairly cheap. Certainly not a premium restaurant, but better than Panda Express I think.
Disclaimer: I'm vegan so I haven't tried most of their restaurants. They do have a steak house, an Italian place, Tex-Mex, a number of cafes, etc., that might be decent. You can find restaurant descriptions and menus on Winstar's website in the
dining section. Few of them are close to the poker room though as it's on the far South end of the casino, but you can walk the whole casino in about 15 minutes.
The Panda Express and Dairy Queen are the closest restaurants to the poker room.