While no one could accuse Hollywood of being unwilling to create sequels to their hit movies, their efforts are nothing compared to game publishers. You rarely see movie titles ending with a number larger than 3 these days, whereas it’s practically the norm in gaming. This isn’t because movie makers are more creative than game developers, but simply because game sequels have more financial success than movie sequels. There are two main reasons for this.
The first reason is that movies have to reinvent themselves with each sequel. You can’t have the same story in a new location with slightly different enemies; a movie must have a new story for each sequel. A different story brings the risk that it will be worse than the previous one, leading to a poorer movie.
Games on the other hand can get away with repeating the same gameplay — even the same story — multiple time in a row. How many times will Link rescue a captive Zelda by finding a sword, a bow and a boomerang along the way? The risks of ruining the magic behind a succesful game is much lower if all you do is create a few new levels.
The second reason is that a movie’s sequel often costs just as much to make as the original. New sets must be built, actors must be paid, special effects must be prepared, etc. To be profitable a movie sequel must be just as popular as the original.
Game sequels often cost less to make than the first in the series: characters are already modeled, enemy AI is already implemented and tuned, the engine is already up and running, etc. Making a sequel to an unprofitable game can actually bring the franchise to profitability, whereas making a sequel to an unprofitable movie is just spending good money after bad.
So that’s why we have so many game sequels: they’re easier and more profitable to make than movie sequels. However, sequels are generally more of the same and cannot really expand the audience for video games. That’s why original games are so important to transform video gaming into a truly mainstream media.