It’s common knowledge in the entertainment industry that the studios, both major and independent, release all of their most likely “award” movies towards the end of the year. This has more to do with marketing and campaigning than anything; nobody trusts academy voters to remember more than a few months back, and this way they can spam the trades with “For Your Consideration” ads to remind people of their great new movie.
This means that you typically see two types of films release at the end of the year. The first is the kind of film that a studio or distributor found to be utterly compelling and unique, and figured might stand a chance as an award contender. This year, Birdman is a good example: something off-beat but interesting that they could push during award-season. On the other hand, you have the “important” film, the kind that doesn’t necessarily have to be good because its subject matter alone places it on a pedestal. These are often the tragic-then-inspiring biopics, or the topical message movies, or the historical event pieces.