My favorite cities for food are Bologna, Osaka, and Los Angeles.
Bologna has the best tasting meat I've had, mainly due to how obsessive they are with the diet they feed the animals.
Osaka is often referred to as the "the kitchen of Japan." I tried to do Kuidaore where you go down all the food stands at night and "eat 'till you drop." I didn't last long but it was fun to see how vibrant and noisy it gets at night. Osaka is also the first time I finally got to try okonomiyaki- a cabbage and batter pancake served with a variety of toppings and best accompanied by beer.
Los Angeles has a great variety of cuisines. Unfortunately it can be hard to find the quality places. All the Asian cuisines are well represented-Chinese in the San Gabriel valley, Korean near downtown, and Japanese and Vietnamese to the south. Of course there are the food trucks which are very social and a lot of fun. It's created a situation where people of a variety of cultures are trying each others cuisine.