I’ll say Smashburger then Whataburger.
In 'N Out is good, but not remarkable. After having had one, I didn’t feel like I had to make a beeline for it the next time I was in California. I have since eaten another double-double, animal style, but mostly because it was convenient, not because it was that particularly awesome.
A&W. Not only are their standard burgers tastier than any other fast food place I’ve been to but they semi-recently added the sirloin burger to the menu permanently which is also excellent.
Here’s another vote for Steak N Shake.
Their fries are killer too.
Bri2k
Cookout (locations in NC, SC and VA, which technically counts as multiple states)
Five Guys
Steak & Shake
The best fast food burger I’ve had lately was at Five Guys. They just opened some outlets in the San Francisco Bay Area. They now beat my long-time favorite, In-N-Out.
They just opened in Northern California a couple of months ago. So it really is coming soon.
Yeah, I was wondering whether Steak & Shake should be counted. It does have a drive-through, but it also has sit-down table service, so I’m not sure whether it counts as “fast food” or not. I think it probably should just qualify.
Their prices are comparable to other fast food places like Whataburger and Fatburger. (A cheesburger at Five Guys is $4.99 and a little cheeseburger–the one I usually get–is $3.49. I don’t think these prices are outrageous, personally. It’s the same price as the better local fast food hamburger joints here, like Edzo’s.) In terms of quality & value, it’s hard to beat In N Out, though. Those truly are great fast food burgers at typical fast-food hamburger prices.
I’ve found that, both for me and my friends I’ve introduced In n Out too, it takes more than one visit to appreciate. It’s really kind of an acquired taste oddly–around my 3rd visit I was in love.
The Cookout! Definitely, when talking about fast food chains.
I’m from the Midwest and it was love at first bite. It’s a good thing I don’t live in Cali, else I’d be about 50 pounds heavier. Whenever I’m traveling anywhere near an In N Out, I have to eat at one at least once (preferably multiple times). It’s not negotiable.
The thing is, I do think sometimes people may have a little bit overblown expectations when they first eat at In N Out due to all the hype. For me, it lived up to the hype (and then some), but I also went into it judging it by what it was: a classic, thin, fast-food style hamburger (which happens to be my favorite style, although I do like a medium-rare 1/2 pound pub burger from time to time.) There’s nothing fancy or crazy about it. It’s just straight-up great fast food eats.
Whataburger, but if we’re going local i’d say P. Terry’s.
Five Guys, by a wide margin.
The closest one right now is up in Thousand Oaks, which, unless you’re in the far east Valley, isn’t TOO far.
That said… I’ve been to Five Guys on the east coast when visiting family, and loved it. Grudgingly admitted it was better than In N Out. So I was excited to take the trip up to Thousand Oaks and try the one out here… and was very disappointed. It was just not nearly as good as the ones I remembered from the east coast. Whether my memory was off, or I was just there on an off-day, or if the quality is just not as good out here… I don’t know. I will give them another try when a closer one opens to me, but for now, I voted for In N Out.
Rally/Checkers. Dripping with fixins.
Culvers.
Steak and Shake is good, too, but I wouldn’t classify them as a fast food joint. Any place where you’re expected to leave a tip for the person who brings your dinner isn’t fast food.
Man, it’s been decades since I’ve eaten at A&W. Do they still have the Burger Family?
Whataburger is far and away my favorite.
Dairy Queen? Dairy Freakin’ Queen? 
But they know their way around a Coney dog. Not one you’d make for yourself, but one you’d get at a walk-up with a gravel driveway while craving The Real Wisconsin Experience. Which can be nice.
There’s gas in the car, Wisconsin is 50 miles away, and Wife gets off at 7:30PM. My daughter will enjoy this.
I’ve always thought Sonic was extremely underrated as a fast-food place, not just for their burgers, but for everything they do. Whenever there’s a thread complaining about or questioning some aspect of fast food-dom, like “Why won’t they serve breakfast all day?” or “Why don’t they have better/more desserts?” or “Why don’t they serve hot dogs/grilled cheeses/real onion rings?” the answer is always that Sonic does, and does it well, too.
That said, since I’ve moved to California, I’ve discovered that the hype about In-N-Out really is true. I’m not a fan of their Animal Style, but a regular Double Double is just about the best fast-food burger I’ve ever tasted. Some people don’t like their fries, but I think they’re excellent, too. I’ve never liked McDonald’s fries, although I don’t remember what they were like with beef tallow flavoring.
Not only is In-N-Out good, they’re amazingly friendly and efficient, and every time I go to the one near me, they’re packed. I can’t imagine why they haven’t expanded tremendously, nor how McDonald’s stays in business here.
That said, I’ve actually started avoiding them, because if I get too hooked, I’ll eat there way more than I should. I’ve even eaten at McDonald’s instead, just because it’s less addicting!