Characters, plot, and world could all carry a game if done right. For character vs. plot, I'll probably side with character because really bland characters can ruin a good plot. On the flipside, a very standard plot could still be enjoyable if the characters are engaging and witty. World building could trump both but it needs to fit the game purpose, like in Breath of the Wild. A vast detailed world could still feel empty without the right motivation for exploring it.