What? All these posts and no one has said Milo’s? Please tell me that the South isn’t the only place that has Milo’s?
If so, then I might have to buy a truckload and send them out to you poor deprived people. 
In fact, I’m dripping one all over my keyboard right now.
Another Whataburger fan here, though it’s been years and years since I’ve had one (1991? 1992?).
For a Colorado chain, I’ve gotta vote for Good Times.
Yummy.
Dick’s in Seattle.
I don’t want to know what they put in their burgers, but they’re addicting. So addicting I think I need a roadtrip to Seattle now…
I’m in the south and NEVER heard of Milo’s
I’m partial to Carl’s Jr., and I’m stuck in a state that has no Carl’s. 
If Red Robin counts, though, that’s my vote. Sadly, we have none of those restaurants here, either.
I spent three years in the DC area and nothing on earth beats Five Guys’ burger and fries. The last time I was in DC I stopped there on my way from Dulles to my hotel. Damn you all for making me think about them.
definitely
Burger King
plain
Burger Street has great burgers!
Braum’s is really good, too.
Whataburger is next on my list.
Sonic ain’t bad at all.
Half-pound of ground beef on a bun! Gotta love Five Guys, I used to be able to walk to one.
The one on Rt. 7? That’s the one I go to all the time. The only complaint I have is that since some stupid Govt. thing came out, they started overcooking the burgers a bit, IMHO. Can’t I sign a waiver?
My husband told me last night that apparently Milo’s is a Birmingham thing. I had no idea.
Pity.
The Five Guys that had been at the Westmont Shopping Center (Glebe & Columbia Pike). I lived off Glebe & S. 9th for a while.
Krazy Jim’s Blimpy Burger in Ann Arbor, Michigan.
Bill Thomas’ Halo Burger in Flint, Michigan.
Five Guys is by far the best. I would venture all the way from Bethesda when I lived there. Good Eats!
Although not fast food, Outback Steakhouse also has good burgers.
Outback’s Burgers suck! (at least in the south) I wouldn’t feed that burger to my dog.
Never been to one in the south. Only the North. I would like to say it’s a regional thing but I suspect they would be similar.
As mentioned earlier, if you’re in Seattle, it’s hard to go wrong with Dick’s. But you can do better – Red Mill Burgers is super tasty, although there are only two locations.
Dick’s has better fries, but Red Mill has somewhat better burgers, really good onion rings, and a variety of shake flavors to choose from. (I go for chocolate/butterscotch, myself.)
I liked Dick’s for the atmosphere (how many burger joints get mentioned in Sir Mix-a-lot songs?) and the food was decent, but is Burgermaster still around? Really good grub and they would hang the tray right on your car window.
I haven’t noticed any New Englanders in this thread. Not too surprising, I guess; I haven’t been able to find a good burger since I moved here.
Not fast food, but another vote for Red Robin’s. Their burgers are SO tender. I know, not the word you normally think of for good burgers, but they really are fantastic. Plus, who else would think to put a fried egg on a burger? Sheer, mad genius, I tell you!