amduser's food photos are alright for blog purpose but for commercial purpose they all fail, and so to most of the food photos here.
from what I observe, the general weakness of all those who posted here, are in their composition. 2nd point of failure is exposure. 3rd point is white balance. 4th point is lighting.
For food photos of commercial quality, please refer to my stock photos.
http://www.shutterstock.com/g/briancychttp://www.dreamstime.com/Goldfries_more-latest-adition_pg1They are also "pictures of my lunch / dinner / supper"
Camera used : EOS 350D / 500D / 550D / 60D / Powershot G1X
Lenses used : 50mm f1.8 / 50mm f1.4 / 15-85
Flash : many of the photos were taken either without flash, or with single flash unit (on body).

for your photos, your composition is pretty decent.
your problem is how you deal with exposure. in restaurant environment, you have to use flash. Without flash it usually looks very bad, unless you happen to be dining during the day and the restaurant has ample light.
You may refer to my article on how to take food photo with basic equipment
http://www.goldfries.com/photography/food-...sic-equipments/I'm sure it'll give you ideas on how to improve your photos.