Hats off to Capcom for designing a game that would become a decade-plus franchise. I can still remember renting (back when there were places to rent games) the first title for my original PlayStation, only to have it scare the hell out of me. Looking back now, the graphics may seem laughable- but nostalgia is always more powerful than its actual referent.
Resident Evil has managed to spawn 5 films, 7 novels, numerous titles with 5 of them coming up in the near future. It's popular enough to have two (count 'em) playable characters in Capcom's most heralded fighting game.
There are longer running franchises, like everyone's favorite plumber duo- but God help them if they make another movie. Not that the Resident Evil movies have been that stellar, but they do have Milla Jovovich in them.