Telling ongoing stories in videogame is harder than you might think.
You might think that videogames would be the perfect place to tell stories that ran for years and years. After all, videogame "actors" never get old, and the only limit is the developer's imagination and what it can coax out of the hardware. But despite seemingly having the deck stacked in their favor, videogames are curiously short on epic sagas. In Issue 304 of The Escapist, Jeffrey Matulef says that the reason so few developers try their hands at long-running stories is that - despite all the advantages - the nature of the medium makes it a tricky proposition.
Many videogame sequels aren't really sequels at all, but rather games connected by motifs and mechanics ... And there's good reason for that; videogames series are hard to keep track of. They take a long time to play, come out on different systems, and date themselves quickly. It's no wonder few rely on presumed knowledge as they don't want to alienate newcomers
Long-format storytelling is also difficult in games is due to hardware incompatibilities. To play Shenmue (legally), you'll have to dig up a Dreamcast and order the disc online since very few retail stores carry games older than a few years at most. De Blob 2 is available on PlayStation 3, Xbox 360, and Wii (as well as a separate DS version), yet its predecessor was a Wii exclusive. Those who own a Wii might be able to track down a copy of de Blob, but those with only a PlayStation 3 or Xbox 360 may not be so eager to jump into a game with a "2" in the title if they haven't played its predecessor.
Matulef says that the Metal Gear series - which has run for nearly 25 years and spanned at least half a dozen platforms - is a great example of the difficulties of telling long stories in videogames. The story of each installment draws heavily from the events of its predecessors, and playing through them all just so you know what's going on is a pretty mammoth task. You can read about it in more detail in Matulef's article, "Where to Begin?"