Definitely bad SERVICE.
Bad service can make even the best food taste terrible. I don't care how good food tastes, if the waitstaff is rude, unprofessional, or ignores me, I will go somewhere else to eat.
But if the food is bad and the service is good, then they will do their best to correct the bad food as best they can (or even comp the meal and ask you to come back again). Plus, you just can't help but enjoy a meal where someone goes out of their way and gives you some extra attention and pixie dust!
The experience is what makes a place.
The exception to this is a place where the food gives you food poisoning or something like that (happened to me at a very very fine restaurant that i had visited several times and had over the top service....then one dose of food poisoning...they will never see me again)...NOT a Disney restaurant.