When it comes down to it, what makes a movie "good" is a matter of taste. Even bad movies have their fans. What makes a movie "influential" is a little easier to try and brute force. Especially when you have Wikipedia on your side.
Massaged into being by the Arg! Team, this massive list ranks the most influential movies of the past 100 years by modeling a theoretical Wikipedia surfer, who meanders through the site, randomly clicking on links. According to the algorithm, the bored little guy clicks a link every second, 85 percent of the time it's a random internal link, the other 15 percent it's the "Random Article" button. The result is a sort of Wikipedia PageRank, and the movies that pop up the most frequently and get the most screentime are the most influential.
Here's the breakdown by year, with the length of the blue bar representing relative influence power:
It looks like Titanic was by far the most influential movie to be released recently, with the original Star Wars film the most noteworthy before that. And, of course, Citizen Kane tops the charts when it comes to weight.
Granted, this is only one way to go about indexing movies, but considering the insane mass of interconnected information that is Wikipedia, it's definitely a valid one. Then again, it's going to have its biases; Wikipedia editors are overwhelmingly male.