Keep hearing about Happiness and have a friend that was going to force me to watch it, but well she's a bit of a slacker.
As for Before Sunrise I absolutely adore the film, and it may certainly be in contention as one of the best films from the previous decade. I enjoyed Before Sunset a lot, but it couldn't live up to the potential of Sunrise. Maybe it is reflective of my age, but I could see a lot of myself in these characters, and damn it's just great.
We had a similar debate on the last site, only the film in question was David Lynch's Mulholland Drive, which would certainly be a film to beat. I may in fact go for the opinion that Mulholland Drive is the best film of the past decade, but well as soon as I'll say that I'll change my mind.
Perhaps a better argument could be a top ten or twenty, or even fifty. There have been some amazing films from America in this time, and I'd say certainly better than most of the limited foreign releases that make their way here. Granted I only get to see a small fraction of the foreign films made, but the US just has them beat. I don't want to start pissing in the face of foreign admirers, because I too am one, but the last several years if I looked at my top tens, I'd be surprised to find foreign films representing even half of the list.