You wrote that "the final results are the same"? Did you really mean to write that they are not the same, but you expect them to be? Anyway...
If the function has a unique global minimum, you should expect the solutions to be the same.
If the function has sub-optimal local minima, there's no guarantee that 2 different algorithms will land on the same minimum, but sometimes they might.
Note also that GA is in the Global Optimization Toolbox, and so is supposed to do a better job of finding global minima than FMINCON. That's further reason for the results to differ if your function has multiple minima.
