I think I put in around 45 hours before I quit playing Okami. This doesn't seem like much, but in games like this I was getting bored at the 15 hour mark.
With that being said, its a long game, but this also caused me to quickly become bored. Gameplay is pretty simple to learn other than the wierd brush techniques you can use on enemies which I seem good idea for a while. Capcom was pretty nice in not making the game too difficult, it's pretty fair mostly on most areas of the game.
Theres some funny parts in this games storyline, but I couldn't stick at it. I will never know what this game was about it made no sense.