Video game franchises are volatile entities. With each successive release of a popular franchise, publishers walk a fine line between pleasing existing fans and attracting new ones. Driving fresh sales with changes to gameplay can backfire terribly, as the fans that made a series a success in the first place may walk away in disgust. Yet publishers are reluctant to ditch previously successful branding, so a profitable series is likely to soldier on until its final iteration resembles its first release in name only. Some games have such valuable pedigrees that even the worst gameplay isn't enough to hamper the critical reception; take the extended technology demo known as Doom 3, for instance.
Other games, however, such as Sierra's recently released real-time strategy game Empire Earth 3, can't survive on branding alone. 2007 has seen a number of superb releases in the real-time strategy genre, and the Empire Earth name alone isn't enough to carry the third game in the series if the gameplay isn't up to par. Given the generally excellent reception of the series' previous release, continued success for the series is no easy task - and by no means guaranteed.