So, to make a syllogism:
Green Lantern can defeat anyone if we assume the integrity of the physical green lantern.
Such integrity can be assumed in a given fight with Silver Surfer.
Therefore, Green Lantern could defeat Silver Surfer.
However, Silver Surfer was responsible for the defeat of Galactus, who can literally EAT WORLDS. I think it's fair to say that in such a battle, it would be on: on like Donkey Kong.
-Ty (this is more fun than orientation)