Depends on what you're looking for.
Sit down leisurely meal: pricey but worth it: IOA: Mythos, at Portofino: Mama Della's (Italian,mmmm)
Counter service:IOA: Thundering Falls Terrace (Jurassic Park), Universal: Richters has good reg and veggie burgers, great fruit cups.
Citywalk: Margaritaville: Sit down, fun, resonable $. Usually no wait except at peak lunch times and after 7pm. You can use your hotel key for prioty seating but it still can be an hours wait.
Also at CW: Pastamore, not the best food but had open tables one evening when everything else was at least an hours wait.
Breakfast: Breakfast buffet at Trattatoria, Portofino or one of the bakeries as you enter either park.