I believe this vary by your state/and or fast food experiences. Since I live in GA i will break down my experiences and then give my first pick.
5 guys : We had one of these. It only lasted 3 months because they apparently were roach infested. (Thank you god for me not eating there.)
McDonalds: I used to love McDonalds but got some raw food there once and needless to say that's the end of that.
Wendys: I like wendys, however our wendy's here does not enforce their cleanliness policy as in they always have girls with nails forever and a day long trying to fix food and I just can not eat food from someone with nails like that. I don't care if you just came from having a mani-pedi long nails in food is a freaking NO.
Burger King: I like the whopper, and our BK is pretty fast, and clean so this is my 2nd Choice
Krystal: This is my first choice because our krystal has always given good service, hot fresh food, and friendly people.