Maybe it's just the fact that so many formulas have been ground into the dirt and also, that the economy has sucked for a good decade, forcing creativity to take a back seat to marketing, but the last decade has been by far the worst in my lifetime.
There seem to be very few fresh ideas, at least, few that make it to the mainstream. Almost everything that has been released is either a remake, a sequel or an adaptation. That isn't always bad, but when it's all you're putting out, your quality level is going to drop off, regardless of box office numbers. I'm sure studio heads have no problem with this, but I hope they don't expect to be lauded as significant artists for it.
As for picture quality, you do know those films didn't look like that when they were released, don't you?
Counting international and Hollywood movies, it's a tossup between the 1980s and 2000s. You're out of your mind if you think the 1970s was the worst decade for movies. It was actually one of the best decades. There were just so many great movies from that decade.