Actually, I didn't become a movie buff with tools like this but with watching the movies liked by the directors of my favorite films. For instance: Pulp Fiction -> Quentin Tarantino -> Bande à part -> Jean-Luc Godard -> Robert Bresson -> ...
In addition to giving you some ideas about films that you could like, this helps you to better see the big picture (no pun intended). You learn about the important movie periods and movements (French New Wave, Italian neorealism, New Hollywood...), you develop a more serious approach to film, and you can live these mind-blowing moments when you notice similarities between two movies done 50 years apart and that looked at first glance totally different.
I already created the engine (which is giving good results for my profile! It recommends me movies that I never thought of). The challenge was mostly to found all the data required by the engine. Now, I must admit I'm procrastinating a little bit for developing the actual web app!
(and thank you everyone for your messages, your projects are awesome!)