I don’t really think there is a best one. They all have pros and cons. Maybe if I was to compare just a basic hamburger (bun, burger, cheese, lettuce, tomato, pickle, onion, mayo, mustard, ketchup), then I would have to say In-n-Out. But everyone has one thing either only that place has, or does better than anyone else with a similar burger.
Basic: In-n-Out’s classic Double Double.
Bacon: Wendy’s Baconator.
Western Style: Carl’s Jr’s double bacon western burger.
Steakhouse Style: Carl’s Jr’s Bourbon Steakhouse Burger (I wish this fucker was a regular item because it is so, so good)
Smoke Meat: Arby’s Meat Mountain.
Chicken: Burger King’s original chicken sandwich.
But I would still take my own home cooked burger to any of these, if I was going to mimic one of them.
