I can not say this is the best, but they do quite a good Cobb salad at Knickerbockers on University and 8th Street. I love a good Cobb salad, so I will be looking to see if anyone has any other nyc favorites. . . .
The very best Cobb Salad in NY can be found at Le Pain Quotidien. I've had them at the 72nd Street location when they're listed as specials, but I understand you can order them off the menu at any location, any time.