The Lives of Others was a masterpiece, but it's definitely not the best foreign film ever. I suggest you check out The Diving Bell and the Butterfly, Amelie, The Good, the Bad, and the Ugly, Seven Samurai, Downfall, and Let the Right One in.
Bicycle Thieves, Battleship Potemkin, The Seven Samurai. Rashômon, 8½. Grand Illusion, La Strada, The Rules of the Game, The Seventh Seal, Wild Strawberries, Au revoir les enfants and Nuovo cinema Paradiso. Just to name a few..
The Lives Of Others is a fantastic film, don't get me wrong, but not "the best non-American movie ever!"
Unfortunately, like most of the Coen Brothers' work, I didn't like it. It takes about an hour for the actual plot of the movie to start, and even then, there's nothing particularly interesting done with it.
This movie proved me once again that I really REALLY don't like Tarantino movies. I loved the 2 first chapters, I was really into it, but after that - borefest. So for me, humour, Pitt and Waltz saved this movie from being horrable.