I attended a game at Petco a couple years ago. The number of food choices was astounding.
I've been to 32 different MLB stadiums. It's doubtful I'll ever get to them all because new ones are built at such a rapid pace.
To give you an idea, I've witnessed games in two different stadiums for these teams: Mets, Phillies, Orioles, Indians, White Sox, Padres, Nationals, Yankees (3).
I've attended games in these cities, but they have new stadiums now: Twins, Tigers, Braves, Marlins.
I have never seen a game in these cities: Toronto, Kansas City, Texas, Houston, St. Louis, Cincy, Arizona.
I took tours of the Houston and St. Louis (old Busch Stadium) ballparks in the offseason, and was in the Diamondbacks stadium for the Insight Bowl. I don't count these, though, because I did not witness a game.