Since this seems to have a lot to do with storytelling and writing, we could consider moving this into the development discussion section.
I know several variations on this, but to me, this is more than anything a "game of wits". Basically, you challenge people to fit stories and concepts into templates - the most use I've been able to observe is pretty much just to put down people's ideas by saying "oh, it's the "everything turns out to be a dream" formula". Either that, or over-analytical applications like some of the plot tags on vndb http://vndb.org/g823 , which are just geeky.
It seems to me that doubting originality is actually kind of trendy these days. In visual arts communities, especially those with a low average age, there is a lot of comments like "that really looks like
character from
game to me" or "your drawing looks really familiar, are you sure you did not plagiarise it from
somewhere?", and in a plenty of cases these happen without any real basis. Unoriginality has become the new deadly sin, and it is cool to be a part of the witch hunt. It is considered neat when someone acts as the authenticity police, and the worst cases even use it as a disguise for insults. I could imagine art is not the only field in which this happens.
I think that in this regard, originality is sort of overly appreciated nowadays. Just because a story is unlike any other it does not mean that it is a good, enjoyable or creative story, and vice versa. A few months ago I read a very original book of poetry that broke the conventions of content, language and even the way the text is laid on the page. Sounds interesting, no? Not exactly. Honestly, it all just seemed like some superficial, drunken rebellion to me.
Then again, I can see where these people are coming from. Far too many stories try to fit stereotypical moulds - or happen to fit in them unintentionally. This seems to be the modern paradox of storytelling: unoriginality is bashed, yet we seem to be less and less creative than before.
There is a good link in the topic
The Writing Nursery about a writer's need for experience, which could be part of the roots of problem. We live in a world of mass produce where stories are becoming mass produce too. This may limit in our view of what a story could and should be. When you have consumed only certain kinds of entertainment for your whole life, it can be very hard to think outside of the box.
For a writer who has this problem, I think the only way to escape it is to simply go out of your comfort zone in both what you read and what you write. If you want to take it one step further, go out and get some new experiences in real life, too! If you do this with an open mind, you will surely find something new and interesting that can stimulate your creativity. This can be an inspiring experience, but it can also be a troubling one, or a conflict with your values that forces you to rethink.
Last but not least, I will offer perhaps my very best bit of writing advice: write what you want to write, not what you want to read. In most cases these two are not the same, and it is not rare for them to be the complete opposites of each other. If you write what you want to and do it with inspiration and love for the story, there is no way it will be truly unoriginal, but if you are trying to copy a story you like even though it does not fit you at all, well, people notice. This includes you during the writing process - you are likely to experience a lack of inspiration and difficulty finishing the story. So write what you truly want to write!