You need both a game with good story and gameplay is better then a game with a bad story and great gameplay or a game with a great story and bad gameplay. --- Victory over Namco destroyer of games through superior fire power! PSN jrr101
Very silly question, most people will say gameplay.
But I'd rather play a game like heavy rain, which doesn't have great gameplay, than watch a movie on heavy rain. Because a game driven by story is still a game.
The real question you're asking gamers is...
Do you prefer an interactive story game
or Do you prefer every other game genre.
It's still not a good question because the margin people will choose will be disproportionate --- "There are TONS of games that look BEAUTIFUL. It's not a matter of polygons anymore, it's a matter of ART DIRECTION now" PSN: Monkeyman0111
You need both, but gameplay is more important. It's right there in the name Video "GAME," not Video "STORY."
I also think that the bigger focus on providing a more cinematic story is part of why games are losing their appeal to gamers and getting more casual - you get less actual gameplay than before, and instead watch a bunch of cool looking videos, even if they're mildly interactive, like in Uncharted.
I've actually found myself bored of PS3 games and dug up the ol' NES & SNES, and I'm having an absolute blast. These games were about gameplay 100%, and they're so much fun to play again.
Gameplay, there are many games and large chunks of genres(puzzle) like Tetris that don't have much or any story at all. A good story is nice yet Gaming has plenty of examples where story means jack, though in all honesty on the opposite side of the fence gaming has plenty of titles with good stories or atmosphere yet rather sub-par gameplay like Bioshock(compared to many shooters and its sequel the gameplay is bad), or Planescape Torment.