So I agree with most of what has been said here. Even if you tried to write exactly the same story, each person is so different, the resulting story would be quite different.
But I don't understand the legalities that are mentioned a number of times on this site. I think there are some writers that are so protective of their ideas that they'll sue anyone that writes fan fiction or anything that comes close to being the same. I'd think in general when things are close you'll have readers that will make the comparison, and when you come up short I doubt you would have much worries about law suits. It's when you're incredibly successful that you have to worry about the jealous authors wanting a piece of your profits by trying to sue you. That being said, it sounds like you'd have more to worry about with all the things you haven't read. But I'm still hoping to understand all of these things better. (You might only have to worry about it when you get to a Jim Butcher or J. K. Rowlings status ... Which means be excited if you have to worry about it! Until then don't worry, and have fun writing.)
I think you're confusing content with concepts. For example, I am writing about a Wizard in today's world. That is the same basic concept as the Dresden Files. But I'm not writing Dresden Files. My content is completely different from what Jim is writing.
Here's a copuple of examples of the differece between Concept and content:
Concept: Giant robots fighting each other
Content: Battletech, Gundam, Macross
Concept: Sherlock Holmes in the modern world
Content: Sherlock, Elementry
Jim doesn't have ownership of the concept of a modern-day wizard. What he owns is the content, his take on the modern-day wizard. My wizard cannot be facing the Summer and Winter Farie, the Black Council, and the assorted foes as Jim writes it. I cannot have gray-cloaked Wardens working for the White Council. While I have vampies, they aren't set up as Red, Black and White Court. The Summer or Winter Knight cannot exist in my world as Jim writes them.
So, I write to make my wizard as different as I can from Jim's with MY take on the world and MY take on the vampires/Farie. I have to create my own form of magic that it my worlds own.
Look at Jim's Furies series -- I head that someone dared him to write a novel based on the Roman Empire and Pokemon. I see both concepts, but I'm never going to mistaken a Pikichoo for a Fury, nor Aleria's legions for Ceasar's legions. Two concepts, different content.
So, I can take any concept I see, but as long as I write it using my own content, I'm fine. Star Wars wasn't the first one to use the "Rebels vs. evil empire," concept. I can use that concept, as long as I avoid wholsale use of Smugglars, ancient order of knights, An evil empire's superweapon, Walking fur carpets, backwater famers who happen to be the hope for the future, and a large armored bad guy.
Concepts are universal: content is the key.
Craig