2000 - 2010
That is the first decade. The movie of this decade is Return of the King. Why? Its simply just a film about poverty, a film about two young businessmen who encounter a loan shark that one of the businessmen do not trust, together the two businessmen must stop the mayor who will get the city under debt. To add to that, the two businessmen have friends that are fighting a political war against the mayor. Now take that story and add: Hobbits, goblins, trolls, dwarves, elves, rangers, medieval weapons, giant eagles and wizards and you have Lord of the Rings. Think about that.
2010 - 2020
Harry Potter and the Deathly Hallows Part Two
You want my reasons, check my previous post. I know this decade has nine more years in it, but I guarantee you, this movie will be the best, unless they somehow manage to make a ninth Harry Potter movie.