Problem with polls like these is a lot of "national" chains are still very heavily biased toward certain regions. I've been all over most states east of the Mississippi (though not so much since my kids were born) and STILL have never seen an In-N-Out or Whataburger. And I'm sure others like me would say the same going the other way.
And while some chains can be great, NOTHING beats a good ol' mom-n-pop grease stand that knows what they're doing and does it well.
So as for "national" chains, Five Guys comes consistently closest to that for me. So many toppings and perfect fries. They can be heavy, but what great burger ISN'T heavy?
But the best burgers I had were from Maxwell Street Station in Chicago (24/7/365 open walkup griddle counter; no-nonsense patties slathered with mustard and grilled onions on a soft toasted bun)... and at the opposite end, Terry's Turf Club (RIP to the original 2018) in Cincinnati - I don't even remember what types of gourmet nonsense I tried each time but they were fully loaded as big as your head, absolutely fantastic, and offered the BEST onion rings I have ever had, hands down.