In the last week I've had 2 of the best burgers. (1) A normal beef cheese bacon and pineapple (i think) burger from Chuckleberrys, and (2) a single mild chicken burger, no mayo, with extra cottage cheese from Steam.
I tried a Quarter Pounder Delux with an extra "100% beef" patty. It makes a good burger and almost as good as a king steer. The only reason that the king steer doesnt come out on top is that i think its too juicy and its classified as fast food. The other two burgers are slightly more wholesome.
The extra cottage cheese makes a huge difference. A burger is all about the flavour. If there is too much bun or if its too dry, or the sauce is too synthetic such that you cannot taste the burger, then its not worth eating. You mightaswell have bread or a bottle of sauce.
There is this little german burger maker in the far corner of the Rosebank Flea Market that also makes good burgers. Its a great burger but it seems to be missing something. They put mayo on the burger to transport the taste but you end up tasting mayo instead of the combined burger flavour. It is definately a high quality burger.
An interesting burger possibility is to have a burger that changes its taste as you eat it. You could possibly have a beef pattie made up of two different mixtures and then somehow get them to bind together. Not sure how strong a bind you could make.