I'm sadly an expert at this.
The "you get what you expect" chains:
McDonalds, Chic Fila, Arby's, Taco Bell, Popeyes
Overrated :
1) Burger King - I'm not sure it's overrated, as much as it just sucks. They charge for everything. More than 1 sauce packet, that's 25 cents. Want to swap out the coffee for a small coke, they add about $1.75 to your cost. Terrible service. Worst fries of all time. Every 6 months I have a need for a Croissanwich for breakfast, and every time I go I remember why I hate the place. Moreso, it's just a way for the parent company to hold real estate. They don't give a crap about anything that goes on in the store.
2) Wendy's - When Dave was alive, Wendy's was relevant. Now it is plain awful. Costs have gone up about $2 per combo meal, while quality has gone down. Service always sucked, but it was manageable. No longer. The whole experience is terrible.
3) KFC - Pure disgusting. How do you mess up fried chicken when it's what you are supposed to be good at. Simply too greasy for modern tastes, and the sides are awful
Underrated -
1) Roy Rogers - Only still around Mid-Atlantic I think. Still have the Double R Burger. And your own fixins bar so you can load up on it