I grew up in DelCo and I have to agree with most people here, it's lacking in the resturant variety. However, I believe if you know where to look you can Find some gems even if they aren't what you'd call "resturants".
My number one has to be Felini's on state street. It's a little Italian place with AMAZING food and atmosphere. The prices are pretty reasonable.
My second is the Dragon Garden in the Springfield Shopping Center. They have the BEST chinese food Second only to The China Aston Inn On Pennall St in Aston (across from the Planet Fitness)
My next few aren't really "resturants" More like amazing take out places. Cimminaras and Gaetanos Pizza, Both on Springfield Rd Have, I think, the best Pizza without heading to Celebrese in the City.