Connections:
-Both are explicitely powerful beings that have false kingship (Gil calls himself the "King of Heroes", claiming dominion over all treasures and kingship itself. But his arrogance and detachment makes him a complete tyrant and an asshole, not a true ruler. While Ghidorah is proclaimed in KOTM as an alien invader who usurps Earth’s natural order. He’s not a true "king" but a pretender trying to impose control over creatures that instinctively reject him.
-Both lash out with overwhelming destructive force when their pride is injured (Gilgamesh despises insolence, punishing those who reject his kingship. Ghidorah is vengeful toward Godzilla, unleashing devastation when challenged.)
-Both are practically main antagonists of their stories (Gil is depending on the episode), covering themselves in gold wrappings (Gil's armour and Ghidorah's armoured skin)
-Both are outsiders pretending to be rightful rulers.
Who are you rooting/betting for if this fight happens?