Here is a very rudimentary formula I came up with for rating a sandwich:
Score on a scale of 1-100:
A = bread
B = meat
C = fixings
D = sauces
.4(A) + .3(B) + .2© + .1(D) = overall score on a 0-100 scale
Each ingredient is weighted based on its level of importance to a good sandwich. Please note that the coefficients can certainly change when dealing with specialty sandwiches (for example, a steak and cheese would have a higher value placed on meat).