Most of the CS restaurants are within the same price ranges, so I feel it's more important to go to one that has food you like. I like Cosmic Ray's and Sunshine Seasons because of the variety they offer.
I think one of the best values for a CS is Earl of Sandwich at DTD. The food is wonderful and it's pretty inexpensive. Where else can you get a cup of tomato soup for 99 cents?
I went with my mom last year (free dining) I am not a huge eater. And my Mom I would say is average.
One day at Peco Bills (M.K.) we split the double cheeseburger meal which comes with a drink & french fries. We paid $1 for an "extra roll" and we split the fries. For us it was plenty..infact we couldn't eat the dessert it came with. The servings seem pretty large to us...
$$ wise, I would have to go with Earl of Sandwich at DTD. We did use the dining plan but I was amazed at the food you got for the prices posted. And the soup (for $.99) was absolutely great!!!