First, not all foreign films are great films. Some are just crappy movies in a different language.

That being said, I prefer foreign films to Hollywood films because they have more substance. Foreign films have better character development and they typically lay the characters out there and let the viewers 'feel' who is likeable. 
Hollywood movies are very 'in your face'. They have the good guy and the bad guy and let you KNOW IT. Example, they'll show the good guy walking his dog, helping old ladies cross the street, being supernice to women, blah blah blah.
The bad guy is so bad, you either hate him on the spot or if you're psychotic, you want to be like him. The bad guy will sell drugs to 8yr olds, beat up women, have sex with 15yr old girls, and push granny down a flight of stairs.

The characters are laughable and do not have much substance. Hollywood movies are so overdone - if they try to portray a woman with lose morals, they'll have her sleeping with 10 plus guys and then some. Hollywood movies are excessive - too much violence, too much sex, too much crap. Yes, there is sex and violence in real life, but come on.

Foreign films are better defined - they delve more into the characters and don't focus too much on unneeded sex scenes when it is not needed. They also stay within the plot - ex: if it's a violent movie, you'll see raw violence. 

There are very few Hollywood movies I like - A Few Good Men is one of them. This is one of the hollywood movies without the sex scene. Purely content.

Foreign films are more intellectual since they are not afraid of showing things the way the are. Yea, some people say they drag on and are a bit slow, but that's why I like them - time is spent on conversation, cinematography and not paying someone 20 million to show their breasts.

Think of it this way - most people who watch foreign movies don't speak the language and rely on subtitles. If the movie is crap, the audience will turn that crap off.