To complete a 1 player game you mean?
More than 10 hours preferably.... if the game is solely 1 player only then it should be longer than that though, unless what you get has lots of replay value.
All I know is I thought Okami was too long, but I also loved the fact that is was so long. I still think it should have been cut a bit though, maybe 5 or 6 hours.
oddly enough LoZ:TP took longer than Okami to complete 1st time but it never seemed too long like Okami did.








