Decent food in Newark...well....that's a tough one. Homegrown is very popular, and I thought it was pretty good until I ordered a tuna steak that was cooked solid. I've never had a bad meal at Caffe Gelato, although people seem to think it's priced a little high. I was surprised to have an excellent burger at Kildare's - typical "Irish pub" atmosphere. (All of those restaurants are on Main St.) So far the best hoagie I have had has been at Rudy's Italian Bistro, in a new-ish strip mall down 896.
Border Cafe is always a good choice! Make sure to try the frozen sangria.
Not far from there is Potstickers, which my husband and I also enjoy. It has a variety of asian dishes - sushi to dumplings to stir-fries. It has a nice atmosphere, but it isn't too expensive in my opinion.
I'm not too familiar with Newark, but Wilmington is quite close. I have to third Border Cafe- love the Mexican items and agree that the salmon is awesome.
In WIlmington, I like the following:
Washington Street Ale house- good food & great beer selection
Orillas Tapas- great tapas options, love the cerviche, nice white sangria
Toscana- very good Italian food
The Border Cafe offers delicious and amazingly priced Tex-Mex. The blackened chicken w/black beans and rice is my favorite. My wife always picks the Chicken Creole which is also quite tasty. Both dishes are priced under $10 and come with free homemade chips and salsa that is the perfect mix of salt and spice.
The Border Cafe rocks. It's cheap and the food is much better than anything else in the area. http://www.bordercafe.com They have a great grilled salmon salad (the salmon is surpiringly always cooked perfectly...not something I can say many places around here) and the chimmichuuri steak is also great. Also all you can eat tortilla chips that are cooked in-house. Newark itself does not have much good food...but then again a lot of what I've had lately in Delaware is not exactly outstanding either. Thankfully Philly's right up the street...