Well, just to throw my two penneth in, I really believe that "originality" in the basest sense of the word, doesn't really exist. We have even had works of complete silence, so if you can tell me a style or genre that doesn't yet exist, (which by definition, can be the only "original" form of composition, then I would love to know it.
In the past, "Classical music" didn't exist either, there was just music. There weren't enough alternatives to warrant a distinction between genres and so the term Classical music was never applied to the likes of Bach, Handle, Mozart, Beethoven etc., in their own times as they were really considered the pop musicians of their day. Now that we do have the distinction, we have to consider who we want our music to appeal to. The vast majority of ordinary classical music lovers, the general public, which is the greatest audience for our craft, still prefers tonal, melody led music with conventional harmonies and meters. It really is a much smaller proportion of the audience, (still a huge number however), that are looking for "new original" music.
Given that on one hand, anything you write, provided it is not a direct copy, is original, and on the other hand, since everything has been done before, nothing is original, then really the only thing that remains, is a question of individual taste, and to which audience you want to appeal.
I think also, if you get caught up too tightly on trying to be original, then you compromise yourself in as much as the reason you are writing, is not because "es lo que sale de los cojones" (this is what comes out of your soul), but rather to try and prove something to either yourself or to others, and I don't think that should really be the motive for producing art, of any description. Although I should also say that ANY motive for producing art, is a valid one, as long as something is being produced that someone else can appreciate on whatever level, then it's good.