Here is guide to help you decide what to eat at Major League ballparks around the country.
I have only been to 9 ballparks and the food at the "K" is the worst I've had. I think the best food would have to be in San Francisco. I was there when they played in Candlestick park and I remember the food was great. The quality and variety was impressive.
I found a map of the food selections at AT&T park where the Giants currently play. Very impressive.