I think there is another argument to be had too.
Do the games' mechanics reinforce the storyline? A game can have a great story and be put on a high pedestal for that alone.
But in how many games does the story get told by the mechanics themselves?
Using Dark Souls as an example, I have read before that Dark Souls overall mantra is about purgatory. Everything in the game is built to be replayed should you die or want to rest. Everyone enemy stays in the one place, the whole world is in this stasis that the player is trying to break free of. The sense of foreboding is driven not only by the environments, but also by the swing of a sword. The labored approach of the characters animation, the heavy steps and the weighty dulled sound effects also add to the feel of the story the player is telling by playing it. From a visual aspect too, the highest point in the world is pretty and white, the lowest point is lava filled and broken down, all to give a sense that you are working through a reference of purgatory.
But the games overall story is told in snippets of items' flavor text, or the very rare NPC you find. So in contrast to traditional RPG storytelling through exposition, in which many of the greatest stories of the genre are told, we have a story that is great to play.
Compare that to what, in my opinion, is the best game story(Final Fantasy: Tactics) which is told through cut scenes and battle text.
All in all, yes i believe Final Fantasy: Tactics has a better story, but Dark Souls is more enthralling because its a story told by you by playing it.