We just got back from our very first trip and were only there for 6 nights, so I can't really offer the 5 best restaurants. In our opinion, using the Dining plan, you get more bang for your buck using the TS credits for dinner instead of breakfast, since it's usually the most expensive meal of the day. We took small breakfast foods (cereal, pop tarts, muffins, etc) in our room and ate before we left for the parks. We used quick service for lunch and the TS for dinners.
Our 3 favorites:
#1 Wave @ The Contemporary. Wonderful atmosphere and fantastic food.
#2 Akershus in Epcot. The price was $350 for our family of 6, had good food, great "princess" experience and the picture included. I would NOT have paid this much for dinner without the free dining plan.
#3 Whispering Canyon @ Wilderness Lodge - Good steak