For underrated I am going for Eggs, you can do so much with them and I love a poached egg on toast.
Secondly is Corned Beef, I have sod all food in the house and just opened a tin, I am now munching a Corned Beef sandwich with mature cheese, gherkins and chutney... I forgot how good it tastes!
For overrated im picking Salmon, I want to like it, i keep seeing recipes that look nice but however much I eat it I really can't bring myself to like it.