Hype doesn't help a game in my case since I never pay attention to it and go in with no expectations.
Sometimes hype pays off, and a game does need some degree of it in order to get people to notice and buy it. However, there is such as thing as too much hype.
Peter Molyneux the master of hype, has been bitten twice by this and one has to wonder if he simply has terrible luck, or hyping a game up is asking for trouble. People gave PM the benefit of the doubt after Fable, but he went and blew it again causing his credibility to dip even further.
Problem with over-hyping is that you can swiftly go from Hero to Zero - ask John Romero.