I doubt Infinity Ward made COD4 knowing it would somehow be this blockbuster that milked a ****-ton of money from people all over the world. And after knowing that it had achieved this incredible popularity, I don't know why they wouldn't milk it for all it's worth if they know it's money that comes easily. They aren't even doing a huge disservice to a lot of people, most people are quite happy with a new COD even if it's almost identical to the 5 that came before it. And it brings money to their families, let's them buy a nice house, a nice car, good food for their kids, and well-needed college tuition when those kids grow up.
I think what's happening now is a pretty natural occurence. There are still gems of gaming lurking around even today, it's just that they're mostly not within the realm of mainstream gaming as they were before. I think that's just what happens when the medium is expanded to also include the tastes of the commonfolk, which I think is what also happened to the music and the movie industry. Point being, once an entertainment medium becomes an industry, more artists will become more focused on profiting from business and appealing to the masses, rather than making some incredible piece of work that only a few appreciative individuals will see.
tldr; What you're seeing today in gaming today is something natural that occurs with every entertainment medium and it shouldn't bother you too much if you actually look for games that you can enjoy out of all the **** that you don't. As far as I can tell, anyway.