Okami is playful in the extreme. There are a few rather surprisingly dark points in the story, but the tone overall is very childish. Oh and awesome.
First off, if its not obvious, you are NOT the person I was referring too, but somehow I don't think you assumed that, ubt just couldn't hurt to verify!
That said..
I can understand a moment or two of dark points, but yeah, the general tone is childish and what not. Just...the concept alone screams that. You have a MAGICAL DOG who PAINTS SPELLS with the help of a little wood fairy thing...really the game is just an elaborate, original fairy tale. Okami plays to this factor, rather than try to work around it, so it ends up being an advantage rather than a flaw.
This goes back to the whole "Dragon Quest is an Elaborate Fairy Tale" argument as to why the games suck. Yes, Fairy Tales aren't necessarily bad, but...the difference between Okami and Dragon Quest is rather stark.
Okami is very childish, knows this, and tries to play to it. Even when its trying to be scary, it feels more in that "Disney Villain" sense rather than genuinely threatening. Actually, it basically is your typical Disney Animated Movie, if spread to the scope of an Adventure Game (this isn't necessarily a bad thing.)
Dragon Quest is very playful but...tries to pretend its not. It pulls these big dark scenes...that utterly fail to have any major impact cause either its playing this cutesy, silly music in the background totally destroying the mood, or cause the games don't know exposition to save its life. Its a Fairy Tale that tries to pretend its not one, and uh, yeah.
Basically, same style, but Okami doesn't try to hide it while Dragon Quest often does (OR alternatively, uses its kiddy style to hide the darkness, which is equally as bad.)
And now, suddenly I realize just how well Okami would work in Kingdom Hearts...just sort of lacks the "Square" or "Disney" aspects and thus will never happen ever...
...which is exactly why Amateratsu needs to make a cameo PC form in Mega Man Powered Up 2! No, I have no clue how this will work, it just does.