This is a tough decision. They are doing something with the FPS genre that is quite innovative, and sounds amazing, so for the first time in a long time, I am just as curious and excited about gameplay as I am about story. There is so much more waiting to do. lol
Games that often fail or are just "B" games, even "C" games like CoD, don't achieve legendary status because they fail to implement all of these things wonderfully. You can have great gameplay and terrible story, or a great story with terrible gameplay, but it won't captivate you like the Elder Scrolls series, or even Halo: CE.
It takes excelling in all those departments to create a game that will stand the test of time.
Who cares about the story? Most great games are known for their innovative and fun gameplay and that's what gives them their legacy. Although there are a few exceptions (Heavy Rain, Journey , etc.) but I think we can safely assume that Destiny wasn't meant to be like those exceptions.