Having eaten way too many servings of airplane food, I can only conclude that the quality of food on airlines depends on which one you fly with. I'll now sum up my experiences with several different airlines (and I mean several). Keep in mind that first class will always kick economy class in food quality and service, but I don't think it's worth the extra money unless you fly under a corporate account.

Good Food

Decent Food Utter Junk Of course, food isn't all that is important. If you're in first class, expect three course meals with a wine list. Very nice. In coach, you get a tray shoved onto your lap with drinks coming afterwards. If the bread is cold, expect the rest of the food to utterly suck. Once, I got an uncooked chicken drumstick on Chinese Eastern. Yech.