Ive had good experiences with all of the 5 guys diners that Ive been too. good fresh fries- no grease, and tasty burgers.
Same experience with Whataburger.
You must have eaten at a counterfeit 5 guys location.
Now theres a local place called hometown hamburgers. Very greasy burgers and so-so fries just like you describe.
2 different locations in the Charlotte area and 1 in Detroit.