If you want to make money and add to the quality of life in the city, focus on developing a pan-Asian restaurant - combining Japanese, Chinese, Korean, and/or Thai cuisines. But especially Thai. Wow, the Thai food options in northern Delaware are just horrible.
I can guarantee that, assuming that you have high quality food, a reasonable price structure, and can serve alcohol, this restaurant will be very, very popular.
Seriously, what are the best current options for Asian cuisines on a walkable Main Street? Pad Thai at Home Grown; no ambience (but very good food) at Number One Chinese; and the very underrated Saigon (which suffers from poor location, but should be more heavily patronized).