Well, I dont know about the best, but here are a few of my personal favorites from each park (but, I'm not sure of the specific names of many of these places)
- Epcot - The food court in the Land has a lot of great stuff that I was surprised to see offered as CS. Plus, the selection is pretty varied, so anyone is likely to find something worth eating there.
Also, there is a CS in England, at the World Showcase, which offers fish and chips, and to me, I'll take that over a hamburger or hot dog any day.
But, to be fair, just about any country in WS has some great selections for CS meals, England just happens to be my fav.
- Animal Kingdom - I would argue that the best CS offerings in all of WDW can be found in this park. I guess thats balances out the fact that there are no TS offerings here.
Flametree BBQ and Tusker House are my personal fav. At Flametree you can get ribs and a number of other bbq treats, and Tusker house offers salmon, chicken and some great, but light, sides. It's almost comprable to a low end TS meal, except you have to wait in line for it.
- MGM - Not really much variety in this park by way of CS meals. A hamburger, hotdog or chicken is the standard fare at just about any CS. However, I find the ABC commisary is about the only location that offers any amount of variety, and the atmosphere is pretty neat too.
- Magic Kingdom - Again, like MGM, not much variety here, but Pecos Bill's is always a nice choice. Also, Pinochio's Villiage Hause (sp?) is not too bad either. But, honestly, hamburgers and fries, or chicken and fish is going to taste the same anywhere you go.
Hope this helps.