it's a mix... stories are important, but not always. When the story is important for the experience, make it interesting. But some games are all about the fun. In those cases, drop the story and don't worry about it, like Left 4 Dead. Everybody is a zombie. It's a virus, 4 guys survived. Period. Why would you care about some conspiracy or evil corporation? Kill zombies and have a good time. I also liked Bioshock, which in fact had a good story hat complemented the game. Great. But video games are versatile and it's a combo. Mix the elements you think necessary and do it. But if you're gonna rely on the story, make it a good one.