We are not fans.
Giant conjures a relatively specific image quickly, and the hard G sound is hard to beat.
Enormous is used up, applicable to a pancake and galaxy alike.
The combined meaning? Big.
What anemic vocabulary produces Ginormous? Synonyms for big should be within reach, people, please— Jumbo for starters. Ginormous is in the dictionary. So? It will go the way of the hell-a prefix, mark our words. It lacks merit! (see above.)