My favorites...
1. Jiko (AKL)
2. Citricos (GF)
3. San Angel Inn (Epcot)
4. Liberty Tree Tavern (Lunch only) (MK)
5. Tusker House (Breakfast, haven't done the other meals yet)
(Of these 5, I'm returning to all but LTT this year. Not returning to LTT simply due to my plans for the parks).
My Least Favorite
5. Sci-Fi Dine In (Not bad, just was in the bottom set)
4. Cinderella's Royal Table (Service and food weren't up to expectations, server constantly spilling juice on the table, right near my camera (no matter where I moved said camera), and it seemed like we were a hassle to the staff in general (we were late due to navigation issues))
3. Hollywood & Vine (Lunch) (Food was mediocre and service was so-so. Was messy as well, but that was expected since there were lots of very little kids there, characters were great though!)
The only places I've actually had a not very enjoyable meal
2. 1900 Park Fare (breakfast) - Food quality and interaction and just seemed like an off day, service was good though.
1. Maya Grill - Loved this place in 2009 both times we went for dinner. 2010 was a different story. Slow, poor service, and very bland food.
However, as noted with Maya Grill, places and tastes change. I'd never simply say "I'll never go back there!" unless it was something absolutely horrible (which, over 2 trips and 2 years, hasn't been the case yet). I may not plan to return the next time I go, but eventually (even to Maya Grill), I'd likely return to give it another whirl.