My favorite food item I've had so far is the beef, lamb, and Guinness stew at the Leaky Cauldron. It has such a delicious flavor and is served in a yummy bread bowl. For some reason I also really love the side salads at the Leaky Cauldron too; there's something extra tasty about the tomatoes in it, although I don't know what makes them so good.
I don't like Three Broomsticks as much, although the theming is slightly nicer, I think. I don't like the chicken--it's a thigh/leg piece (I guess that's what it is), and I just don't like that part of the chicken. They have an amazing apple pie, though, with raisins in it! And fizzy pumpkin juice! The apple pie is HUGE--you could make a meal on just that and a fizzy pumpkin juice, if you weren't overly worried about nutrition.
I also love the onion rings anywhere in the park. They're just the right amount of crispy but not greasy, and the onion is perfectly gone from crunchy to tender but without going all the way to mushy, and it's just so slightly sweet. A simple thing, but so good!