Animal Kingdom: I REALLY like Yak and Yeti (especially when you ask for a seat on the second floor), though if you want a quick serve, Flame Tree or Satu'li are solid options; Nomad Lounge is another good option if you want to keep it light and just do snacks and drinks to hold you over to a larger meal elsewhere
Magic Kingdom: Liberty Tree or Skippers are solid choices; I like Liberty Tree just because the food feels so much like "home" and just the fact that you can go there and sit down, order some drinks and then the food just starts arriving without you even needing to think about it is nice; however, BoG is a great option for first timers, like others have said, it's not something I do every trip, but it does have that "wow" factor that is neat to see with first time visitors, CRT is the same way, but unless you are sat by the window, it's just not the same (especially for older guests... plus, it's pretty expensive for what it is).
Hollywood Studios: Prime Time is a great option... the waitresses don't get quite as into it as they used to, but again, it's that "home style" food that feels really nice on vacation, plus it's still fun. Sci-Fi Drive is fun too, I'm just not as wild about the food there.
Epcot: Can't really go wrong with most of the choices there...
Hoop Dee Doo is a 100% MUST for me (on EVERY trip.. first timers or not).