There is certainly a sense of "it worked once, lets make it work again" in Hollywood when it comes to themes for TV series. Sure, there are some formats that are always hanging around -- medical dramas, legal/cop/crime stories, comedies about families/parenting -- but whenever something vaguely new or unusual comes along and strikes a chord with viewers it almost always get replicated by all the networks.
Most folks trace the current sci-fi craze to Lost. There is little question that interest in that genre is part of what made NBC take the plunge with Heroes. It also helps that almost all of the biggest movies of recent years have been at least somewhat in the sci-fi realm.
Really, the TV networks trying to duplicate the success of one show is no different from what happens in the movie business. Iron Man, Batman, and other current superhero movies got their big-budget go-aheads from studios that saw the monster success that was Spiderman a few years ago.
All these things come in waves. We are currently in a big sci-fi wave. It will fade at some point. Sci-fi won't go away but something else will be on top for a little while and you'll see a lot less sci-fi/comic book stuff on TV and in theaters. Then, whatever the new fad is will fade and sci-fi will come back. It is hardly rocket science to see how this stuff works.
Want more examples? The current reality TV/game show craze on TV is largely a product of the huge success of Survivor (summer 2000) and Who Wants To Be a Millionaire (fall 1999-spring 2000). It is just how the entertainment biz works.
-Jason
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