In the 1950s and 60s, a fair number of great movies were made, still considered classics today. Some Like it Hot. Casablanca. The Apartment. Rebel Without a Cause.
These movies weren't "art" movies or "alternative" movies, or unusual productions by unknown directors.
They were mainstream.
They featured the hottest stars of their day.
How often, today, do you see a mainstream movie that's really good? One that you think people will still be keen to see in 40 years?
What's changed is that Hollywood movies used to be about people.
Today, almost every movie is about situations. Car chases. Special effects (which sometimes are just meaningless light shows -- not even situations).
Many successful movies in fact are parodies -- sometimes not even of other genres, but of themselves. Look at Johnny English, a parody of the Bond genre, which is itself a parody of itself. These movies work because they laugh at themselves and, by extension, all of Hollywood.
Why? Because Hollywood produces nothing to take seriously -- at least not as mainstream entertainment.
Hollywood is a victim of its own success. The star system, which used to produce acting of great character, has become overblown to the extent that even mediocre actors can be marketed as stars, and their inability to portray anything like real people convincingly means that frills and tinsel in the form of car chases etc. have to substitute for real entertainment.
Marketing has replaced imagination, because the process of identifying real stars is too risky.
But there's hope for the future.
Some of recent animated movies have shown the potential for replacing human actors by animation. We aren't quite there yet, but we're getting close. Once we factor out the costs of manufactured stars of mediocre ability and maximal fees, movies can return to imagination as their currency.
Screen Actor's Guild, beware.