Lol I was expecting this question.
I read here on vgchartz following sentence:
"Visual novels are very popular in Japan. For some reason, people do not seem to be making the connection, but thats exactly what Heavy Rain is. Its a visual novel done in the west, with western budget and art and GFX. "
HR is an experimental game it could very well be a decent success for a western game if the Japanese accept this westernized style. They dont like FPS and most of the western stuff but maybe this ?
And I think it could even shift some hardware due to its uniqueness.
Its just an uknown factor yet we dont know how it will perform. Thats why I listed it. Its special and it could attract some people if it is what it could be.