Certainly I agree that every decade seems to have its own motif when it comes to the movies. This past decade was certainly the rise of the superhero movies, with cartoon adaptations being the understudy. But when you say 20 out of 100 will be worth watching, I really hope you mean out of every ten years. I can't honestly say I've seen more than 20 movies in that last ten years, mostly because while I am not a snob, I just haven't heard of many movies that really grab my attention as being something I'd want to watch.
Basing screenplays around popular books and movies is fine. Obviously, they do it because the studios know they will already have a built-in audience, and it's not a huge risk to them to make the movies because they anticipate they will make their investments back. I'm not all that crazy about them re-hashing old movies to try and update them for a modern audience, regardless of their actual financial outcome (such as War of the Worlds and The Day The Earth Stood Still). They might make a decent reproduction, but often they do not live up to the original. Take The Honeymooners movie they made a while ago where they replaced the original cast and made them all black to appeal to a niche audience. That didn't even make much sense, and apparently didn't make enough money to warrant a sequel. In situations like that, I'm glad. Ok, you proved you could do it and some people would see it. I'm just happy they didn't feel the need to continue to shove it down our throats like all that Tyler Perry shit. Did his plays really need big-screen counterparts, and a spin-off series of television shows? Not in my book. Basing movies on loose stereotypes is just lazy sociological writing that takes basically no imagination, but comes down to the bottom line: will this dumb idea make money? If that is ever a consideration you must make as as studio head, I say skip it in the future. Why bring your credibility into question to make a quick buck? Integrity is a lost trait these days, and it seems more and more studios and producers are more interested in making money than making a good name for themselves (I'm look you at you, George Lucas). I can't really suggest a good idea for a great movie, but it doesn't appear that a lot of people can do any better if the current movies are any indication.
Good articles, Bob. Keep it up!