Yes, there are nice seafood and Italian restaurants on WDW property.
Our favorite Seafood restaurant is Fultons, located at Downtown Disney Marketplace, adjacent to Pleasure Island. Can't miss it... it the large steamboat. The variety of fresh seafood this restaurant has to offer is phenomenal. It is a bit pricey, but well worth it
Our second favorite is Narcoosees, located on the Seven Seas Lagoon at The Grand Floridian. Wonderful steak and lobster, not to mention the awesome mussel appetizer. Highly recommended are the Mahi Mahi, roasted grouper, rare tuna and sauteed shrimp over angelhair pasta. The view is outstanding, as well
Tied for 3rd would be Coral Reef at the Living Seas in Epcot, and Cape May Cafe (although this is a buffet, and it has more than seafood). If you are into steamed shrimp, clams and mussels, in massive amounts, this is definitely the WAY TO GO! You can also add on steamed snow crab legs at an additional cost. Coral Reef has delicious seafood soups, great seafood pasta and nice fish dishes such as pan seared swordfish. Also, the wall sized aquarium is very entertaining while waiting for your dishes to arrive.
As for Italian... I am a big fan of Northern Italian food and have been extremely happy dining at L'Originale Alfredo di Roma Ristorante (affectionally called Alfredo's) in the Italy pavillion in the World Showcase in Epcot. We have always had great food and impeccable service. The House Specialties include Fetticinne Alfredo, Pasta 3 fagioli, linguine al pesto, vitello alla Milanese, Pollo alla Nilanese, Pollo all Parmigiana and roasted lamb chops. Portobello Yachtclub at Downtown Disney, located next to Fultons is also very good. Again, this features more Northern Italian specialties such as breaded ribeye, charcoled grilled shrip on rosemary skewers, chripy tin crust pizza appetizer suge as vegetarian pizza, and 4 cheese pizza with sun dried tomatoes.
For Italian food that is more Southern/Mediterranian, then I would suggest either Palio at the Walt Disney World Swan. Some of the specialties would include Veal alla lemone, a scallopine served with lemon butter and liguine, Saltimbocca all Romana, veal medallions topped with proscuitto and sage, served with risotto, and veal picante alla marsala. Another good place in Mama Melrose at Disney MGM Studios, located back need Muppet Vision 4 D. This specializeds in pasta and designer pizzas.