Here are some of my favorites for atmosphere inside
Disneyland:
Rancho del Zoccalo: Decent Mexican food, plenty of nice outdoor and indoor seating. Its right in Frontierland and at some tables you are very close to the tracks of Big Thunder Mountain and can see the trains as they come into the station.
Golden Horseshoe. You can have chicken strips, fried cheese and chocolate cake and watch Bill Hill and the Hillbillies perform their hilarious show while you eat. Check the times guide, they play every day, multiple times per day. If you arrive 45-60 minutes early you can wait in line, get your food and be seated by showtime.
Plaza Inn: I like this one because its a very pretty, Victorian decorated restaurant (I think I read once Walt's wife Lillian decorated the Plaza Inn). Its a buffeteria and the portions are HUGE. They have a fried chicken dinner that has three pieces of fried chicken, a biscuit and green beans. I think its about $12. They also have pasta and pot roast that are huge portions too. We can get two of those for our family of four and be plenty full when we're finished. They also have nice, dinner salads. My husband and I can easily share one dinner salad and one meal. They have plenty of indoor and outdoor seating. Note: this is a character meal at breakfast only. They also have a birthday party for kids each afternoon so the outdoor seating is off limits during that time but the indoor seating will be open then.
French Market: Its in New Orleans Square, they have a fried chicken meal too that includes a salad. Lovely, outdoor seating and they play live jazz.
Riverbelle Terrace: Located in Frontierland right on the Rivers of America. We love to have breakfast here, they have Mickey shaped pancakes and a wonderful view of the river. At night if you are very lucky you can score a table, have dessert and watch Fantasmic.
Redd Rockets: As others have said, huge portions. Not as much atmosphere, its very noisy but its decent food and a great place to eat while you wait for that Space Mountain fastpass to come up! I really like their pasta and salads.
Carnation Cafe is a very pretty full service restaurant. The prices aren't much more than cs (but you'll have a tip) and it has good sized portions that can be shared. It is all outdoor seating, right on Main Street. You can make a ps for that one, they also take walk ups but you may have to wait a bit.
In DCA we love to eat over in the Paradise Pier area. There is a Mexican place called Cucina Cucamonga (sp?) and a bakery there. The bakery has salads, sandwichs and soups. The bakery has indoor seating but there is also a nice outdoor seating area between these two places and a Margarita stand too if you'd like drink! At night, it is lovely out there as you can see the beautiful lights of Paradise Pier on the roller coaster and Ferris Wheel.
Taste Pilots Grill has good burgers and chicken sandwiches and a fixings bar. Its right next to Soarin so a good place to eat in conjuntion with that ride.
Since DTD is right there you have lots of nice options. We love to go to Naples in DTD at night, there is a wonderful violinst that plays right outside that restaurant and you can sit outdoors and enjoy the lovely music on the nights he is there. Also, Naples and Tortilla Joes have takeout windows with great prices, big portions and there is plenty of places to sit around there. A bit less expensive than park food and there's always something going on and great people watching while you eat.
Near Disneyland is Mimi's which has great food, great prices and huge portions for breakfast, lunch and dinner. Its about a fifteen minute walk up Harbor.