Speaking of rpgs and action_adventure games in general, i consider this complex area of the gameplay as important as a story, battle system or soundtrack can be. "Why would it be so relevant?" or "It is even gameplay?" are obvious questions that could derive from my last affirmation, and my answers would be, yes, it is relevant and yes, itis gameplay. A good mythological reference sets the background, and ultimately the introduction for a game. Also, in my opinion, it makes a soundtrack much more natural and enjoyable, i wouldn't be expecting a game based on, for example, japanese myths (like Okami) to feature western-like sounds and music, it would ruin the game, at least for me. And for those whoes haven't noticed yet, the myths are already a part of the gameplay; i cannot imagine myself playing God of War without know anything at all about greek mythology, Castlevania ignoring all the time the vampire reference found through the story (any of them), or final fantasy withouth notice that every piece of weapon (at least the powerful ones), bosses, summon monsters, etc., are based on some kind of myth; its simply 50% less fun.
I know that most of people tend to ignore this juicy and deep part in a game, but for those whoes doesn't, enjoy, every game is better that way.