Games are becoming more and more dependent on the CPU for physics (GTA IV and Crysis as great examples). The more resources available, the better they'll play and the better they'll look. Crysis and GTA can put a quad to 75% ulitilization and beg for more.
As the quest for higher speeds has declined among Intel and AMD, since they realized that anything significant would be too costly to develop, more and smaller cores have been the answer. It's up to software developers unfortunately to take advantage of them by writing multithreaded apps.