Games are, by definition, an interactive media. That is why I say that gameplay is the most important aspect of a game. If you want great visuals, why not paint something? If you want great story, why not write a book? If you are interested in audio, why not compose some music, or a radio drama? If you want a great combination of visuals and audio and story, why not make a movie? Games are about interaction, and that interaction comes in the form of gameplay.
As I said above, there are some games out there with mediocre gameplay and great stories that are popular, and get played, and are made better by the story. I would put the Final Fantasy games in this category -- the gameplay isn't that great, and remained pretty much the same from FF IV all the way through FF IX, with some minor variations (though some may disagree with me). But can a game with truly terrible gameplay still be a good game because of a strong story? Can you think of any games that fit that criteria? Great story, terrible gameplay?
On the other hand, can a game with a terrible or nonexistent story and great gameplay be a good game? I think the answer is obviously "yes." What kind of story does the original Super Mario Brothers have? "The princess is in another castle?" Terrible story telling, but a great game. Rez is a game without a story that is a great game (though it does have strong audio and visual, which I will get to in a moment). Castlevania: SotN has great gameplay, and a downright stupid story, terrible voice acting, and a pretty good sound track. Sonic the Hedgehog has great gameplay, no story, and mediocre sound. Shadow of the Colossus has virtually no story, and is all mood and atmosphere, though it also has unique gameplay, which makes it interesting.
So, while story can enhance a good game, or even bring a mediocre game into the realm of good, I don't think that it can make a game. A game with truly terrible gameplay will never be good, while a game with a truly terrible story could be good. I would make the same arguments about sound and visuals. Great sound design or visuals can enhance a good game, and improve a mediocre game, but they can't fix poor gameplay. Which gets us back to Rez -- the gameplay in Rez is a bit ho-hum, and is not all that unique, but it is not bad -- it is actually reasonably good. Without good sound and visual design, Rez is a run of the mill on-the-rails shooter. With good sound design and visuals, Rez is a really good game.
That is exactly the point that I am trying to make -- games are about interactivity and gameplay. If the gameplay is poor, nothing else matters. But, with the right sounds, story, and visuals, a less-than-great game can be good.
I will finish by reiterating a question from above: Can you name one game with a great story and terrible gameplay that you would consider to be a good or great game? Name just one...
xander