Galactus should be portrayedd as he is in the comics; a somewhat arrogant, omnipotent being. Again, MUA as a reference is perfect.
What makes Galactus the character he is, is the manner in which he's portrayed. His size is relevant because it literally makes him larger than life. Just as we see Galactus in the comics; assembling his machinery; suspended high in the sky--with neither a care or interest in the destruction and loss of life he is about to cause. His indifference to the beings and planet he is about to devour make his character. Galactus simply goes about his business as if the inhabitants don't exist. Perchance, the inhabitants do gain his attention, they will either regret annoying and delaying Galactus from his most important task of feeding his hunger or gain an audience with him--which may still prove futile considering the arrogance and indifference of Galactus.
Again, Galactus must be portrayed as he is in the comics to be successful, otherwise you wind up with yet another poorly interpreted Marvel character.
And for heaven's sake; PLEASE DON'T LET STORY AND FOX TURN GALACTUS INTO A BEYONDER LIKE CHARACTER TO PUT A HUMAN SPIN ON HIM.