5 Napkin Burger
After trying many a juicy patty, I always return to 5 Napkin Burger. There's just something about their original 5N Burger special sauce with the caramelized onions that make it unmatched, and the meat melts in your mouth.
(It's also great without a bun over one of their salads if you're gluten-free!)
7th Street Burger remains worthy competition, but alas, no Hell's Kitchen location.