In terms of working intelligence Golden Retrievers are exceptional, which is why they are capable and popular guide dogs, therapy dogs, sport dogs and gun dogs. They do tend to take a while to mature however. I think it's a combination of their natural personalities and untrained temperaments which make them so goofy as companions.

Many breeds shine in different departments and in different conditions too. I've owned a few dogs, the brightest I'd say I owned would have either been my Blue Heeler or Doberman, for reference I've owned two German Shepherds, an Aussie Shepherd, two Labradors, an English Staffy, a Jack Russell, a Border Collie, a Great Dane and a Mastiff x Rhodesian Ridgeback. My Doberman was definitely the most generally intelligent, very mature and regal dog who really shone in most areas. Blue Heeler was probably the quickest to learn, required very minimal training and picked up on things quite intuitively. Border Collie and Labrador would follow, although both had pretty major derps which wouldn't quite allow them to make that top tier.