the way Case West plays out indicates that the apparent canon ending of Dead Rising 2 isn't the best (i.e.:  Most difficult to earn) ending, but rather one of the second-tier endings.

Frank's contact at Phenotrans turns out to be Isabella from the first game, and the company has had a cure for a while, but keeps it hidden since they can make more money with Zombrex, which requires a new injection every day.
 
People are apparently upset because it sets up the plot for Dead Rising 3 and doesn't provide much more closure than the 2nd game already had.  Frank wants to rescue Isabella from Phenotrans, and Chuck wants to get the cure from them, now that Katey is safe (from zombies, at least).  It implies that the sequel will be the two of them taking down the company.  They also reveal who will likely be the main antagonist, a wheelchair bound woman who heads up the company and was bitten by a zombie (on the face!) herself, and needs Isabella for a "secret project".