Disney Springs - Wolfgang Puck Express is great. I love Earl of Sandwich, but it never agrees with my husband (he had his gallbladder removed a few years ago and some things just don't work for him anymore). We love Ghirardelli sundaes (the brownie sundae is best), but we have one in Chicago we can go to anytime, so we don't usually go at Disney Springs. We enjoy splitting a caramel apple from Goofy's Candy Company. They will cut it for you if you ask.
MK - BOG lunch is fabulous. BOG breakfast is something I would call poor value. We were unimpressed with Columbia Harbor House, but we went at lunch time when it was packed, so YMMV.
Epcot - I thought the Cronut just outside the Canada pavilion was delicious, and I also really enjoy Karamell Kuche in Germany for snacks. We liked Kakigori with the sweet milk topping in Japan.
Hollywood Studios - They have very poor quick service in my opinion. We usually pack peanut butter sandwiches and eat a table service meal outside of the park. We do, however, love some of the snacks. The Carrot Cake Cookie is great, and the Butterfinger Cupcake is the best I've ever had. You can find it at both Starring Rolls and at Trolley Car Cafe (Starbucks). At TCC it's renamed - I can't remember the exact wording but it has Toffee in the name.