Star Trek has the same problem. Episodes were produced independently, which means the state of the universe has to be reset at the end of each episode. More recent American series tend to have a season-long plot, though.
I think of the endless episodes of Naruto, Pokemon, Conan, One Piece.
Doom didn't have a plot. Tetris didn't have a plot.
Also, if you want the game to have a MEANINGFUL plot, then you have to pretty much make the game linear, which isn't the point of a game.
Trying to make a game like a movie is missing the point.
When I hear things like "This game has 20 hours of gameplay!", I cringe, because if it's a really good game I want to play it more than 20 hours (one reason I like roguelikes).
Other media example: Some people love serial television, other love 2 hr movies. Some people like both for different reasons.
It's okay for people to like what they want for whatever reason they have.