I'm not putting down food in other areas of CT. There are some formidable foodie scenes elsewhere. Westport, Milford, West Hartford, Middletown, Hartford, South Norwalk, Stamford, just to name a couple.
But nowhere else in the state has the concentration and sheer number of goodness as New Haven. It's almost as if the culinary influence is so powerful, it positively affects the communities around it (Milford, Hamden, Branford, etc.). And above all, I find that the hype is usually deserved, vs. some of the higher end eateries in southern FFC where the glamour and cachet outweigh the actual food.
Why New Haven? Besides having a well laid out, dense urban core and a diverse population: it's the higher education. It's our quintessential college town, and like Cambridge in Boston, you tend to have a huge concentration of restaurants and bars when you have so much young discretionary income walking about. The opening of Gateway downtown with 14,000 more students circulating the streets will only further the development of new eats.
Probably the most well known food aspects of New Haven are its pizza (Pepe's, Sally's, Modern, BAR) and its place as the originator of the hamburger (Louis' Lunch). Caseus and its truck have also achieved some notoriety on TV. But it goes beyond that to a long list of greats which have been mentioned on this board ad nauseum from a long and diverse list of cuisines. I'm not going to attempt that now.
The city keeps adding new restaurants every year and, compared to 15-20 years ago, it's made leaps and bounds. As long as crime is reduced in the next few years (which ironically happens mostly outside of the places we tend to eat) and development continues, we will have more goodness to look forward to in the future.