Theme parks have always looked to broaden their appeal to offer new food selections beyond just the traditional hot dogs, hamburgers and pizza.  Adding specialty and chain restaurants that could provide unique food options became a big trend with various restaurants setting up shop in theme parks.

When Great Adventure's entrance was moved from the end of Dream Street to the Fountain area in 1976, the focus of the park changed a lot with new shops and eateries added around the Fountain to accommodate the new traffic patterns.
For many years one side of the Fountain was home to Paul Revere's Hats and a small stand named Franklin's Ice Cream Shoppe. For the 1998 season those small stands were replaced with a major new restaurant, the Colonial Cafe. The Colonial Cafe helped round out the food offerings at the Fountain, supplementing the existing pizza and burger restaurants.  It also expanded the park's food service window by offering breakfast foods and drinks to guests before they set off for their day of adventure in the park.
The Colonial cafe lasted through the 2000 season, becoming the Central Park Deli in 2001. The new name helped differentiate it from some of the other restaurants in the park, letting guests know simultaneously where it was located and the unique variety of food offered that couldn't be found in other park food outlets.
Colonial Cafe Names
Through the Years

Colonial Cafe

Central Park Deli

Carnegie Delicatessen

Main Street Deli

 Main Street Pub
In 2007, the new Six Flags management decided to focus on adding name brands to the parks- the idea being that if people saw a brand they knew, they were more likely to want to buy the food.  Central Park Deli became the Carnegie Delicatessen at Six Flags Great Adventure, offering the famous sandwiches and deserts from New York's most famous deli.
The Carnegie Deli was a hit with guests offering delicious and unique food options in the park which was a welcome change of pace for guests looking to have something besides pizza, fried chicken and burgers. 

The food stand proved so popular that in 2008 the adjacent merchandise location which previously sold mostly hats was converted into a quick counter service facility called Carnegie Express.  Short-lived, the Express location was discontinued when that stand was demolished to make way for the Cyber Cafe in 2009.
For the 2011 season, the Carnegie Deli name went away, and the restaurant became the Main Street Deli, a generic and less fancy version of the food outlet. A quickly created Main Street Deli sign was short-lived, getting replaced with a more permanent version featuring a unique new logo later in the season. The name was changed again for the 2012 season (though the logo remained the same) with the restaurant taking on the new moniker Main Street Pub.
As a first food stop for guests arriving, a central meeting point for families to get lunch during their day, or a place to grab a final bite to eat before leaving the park, the Colonial Cafe facility continues to be one of the most popular eateries in the park today.