Natural ability plays at least some role. I'm never going to become an amazing mathematician considering I literally cannot understand the number seven. I could still do well at other things though and so can anyone.
Einstein wasn't just amazing because of how smart he was, but how he changed the world. Anybody has the potential to change the world, even if they're dumb as a post. In fact, people change eachother's worlds every day without even knowing it.
I think anybody can achieve something if they put effort in and have passion, but what they achieve depends on heir nature, natural abilities, etc. And sometimes, the little things mean a lot more than you might think.