5 Guys is pretty good for a chain, as is Braums (the Purcell location makes some really good burgers). The best burgers in central OK, though, are made in The Diner on Main St. in Norman. The only problem is that they're only open for lunch, and parking in old Downtown isn't exactly plentiful.
Wasnt a fan of S&B's. Flat Tire is one of the better one's as is H&H's. Smashburger and 5 guys are decent. Havent had Nic's, Bunnie's is ok, but anticlimatic, prefer the onion burgers at H&H.