In Santa Fe, New Mexico, it's Bert's Burger Bowl (slogan: One Location Worldwide!). Get the green chile cheeseburger. For non-Southwesterners, chile in this case means the actual vegetable (in this case the green variety, as opposed to the red) that is cut into strips and grilled, not the beef/bean/spice mix sometimes spelled "chili" or "chilli". Anyway, the green chile cheeseburger is awesome. The fries are fine, but not why you go to Bert's.
In El Paso, Texas, it's the Charcoaler on North Mesa Street. This place has the best burgers I've ever had, hands down. There's no seating, it's strictly drive-through, with a big U-shaped drive that leads right to the window, which is huge, and you can see the burgers being grilled over open flame. There's a space of lawn in the "U" that they sometimes spray-paint green in the winter (sometimes not). They have a special barbecue sauce they put on all their burgers, and it's astonishing, incredible, magic. Their fries are thick cut and done just right, and you can top it all off with a large lemon Dr. Pepper poured over shaved ice, not cubes.
I am now agrieved that I cannot go there right now for lunch (been a long time since I lived in EP), but I am willing to make that sacrifice to spread the gospel of Charcoaler. Go forth, eat well!
Warrior Poet