Wow, I agree with Joseph. Chap-a-Nosh has the closest burger to what KD had. However, that doesn’t make it the best. It’s a cheap fast-food burger.
There are plenty of places to find a good burger. Just realize that you will likely pay far more than you would for the fast-food burger. A beef burger at Chap-a-Nosh is $3.99. A Super Burger (like a KD Burger Delight) is $6.99.
At Gotham Burger (since it was mentioned before), a regular burger is $9.50. Their specialty burgers are more.
You get what you pay for.