The problem Koei has with (western) reviewers is that, to the untrained eye, each new instalment seems to add so little to what's gone before.
You only have to type 'warriors' up in the top left corner to see a) how many of these battlefield epics Koei has already brought out, and b) how each successive instalment seems to sap a little bit of each reviewer's generosity. Yep, the marketing survey simply assumes that you've bought a sequel. The generic marketing survey that falls out of the Samurai Warriors 2 manual asks 'what motivated you to purchase this game?' It goes on to offer a selection of choices, but the one that stands out is: 'Liked the original'.