Read the article [http://nyti.ms/fbxQBI] in the New York Times about this question and thought I'd share my two cents with you.
From my experience, I agree that there are only so much improvement that we can all expect from any training that we do. But I get worried when articles like this give the everyday person an excuse to not even make the effort. If I believed that genetics dictated the physical abilities of everyone, I mean, what would be the point of trying?
This is what I've experienced and what I've seen from other athletes. Genetics do play a big role, but they are not a be all to end all. If I were to put a value on how much certain aspects of running success, I would put it at 50% of it is genetics. 20% of it is training. 20% is age. 10% of it is diet, weight and/or lifestyle [amount of sleep, personal hygiene care, healthy choices, etc.]
My grandmother used to say that you can't make a silk purse out of a sow's ear. That may be a crude analogy but I think you can probably make the best pigskin purse by applying the same sewing technics on the pigskin as you would the silk. Meaning that you can get the best of what you've got by applying the best effort.
I've finished many a race behind a runner with better genetics than me. But I've also finished ahead of my share of runners that had genetically better VO2 Maxes than me. Give me a runner with a VO2 Max of 82 with no training at the start of a marathon, and I'll bet you that my VO2 Max body of 48 finishes that race 9 times out of ten before them [if not all ten]. If the genetically superior person does not train their genetically superior body, it limits it ability to provide superior performance.
So I agree you can put in what God left out. But you can play the best hand with the cards you were dealt.