Movie Dialogue- Past and Present

So now having watched several classic films in my film class right now and also keeping up with some of the more recent films in theaters, it is most apparent that film dialogue has changed drastically between the classics and today and mostly for worse. The dialogue in such films as The Big Sleep, The Philadelphia Story, North by Northwest, Vertigo, and Mr. Smith Goes to Washington is overall really witty and the quips are so strong you can't help but laugh. Clearly, this type of writing in films nowadays has gone away and been replaced with childish ignorance much of the time. Occasionally you'll still find a gem where the dialogue is very strong, but even some of the stronger writing nowadays can be overfilled with cliches. Admittedly, it's harder to write dialogue into a film these days and not write some cliche material since new films are likely to only take some sort of material from their predecessors, but I say to any screenwriter, if a section of dialogue comes off as funny when it was meant to be serious, either rewrite that scene or cut it out. I bring up a perfect example of this in the recent X-Men: First Class directed by Matthew Vaughn. There is some dialogue with the Russians and the Americans in regards to the Cuban Missile Crisis. The background music clearly brings the emotion that the scene is supposed to be a suspenseful, dangerous one, yet I could not help but laugh at the way the scene played out because of the dialogue. My only thinking was that seeing Bryan Singer's name in the writing credits of the film is that the specific scene to which I refer was written by him, speaking from experience with Singer's Superman Returns starring Brandon Routh. Needless to say, if you see a new film in theaters and actually believe the dialogue, more than likely it is a great film and will probably be up for an Oscar nom in its respective year.