I was watching Moon (2009) the other day and it struck me that there's been a lot of really good mind-bending movies out in recent years..... and there were hardly any during the 1970s and 80s. We are truly living in the Golden Age of Cinematic Mind Blowers. I'm not talking simply "science fiction"; I'm talking "this movie literally hurt my brain!"
The 1960's had precious few mind blowers - the penultimate being 2001: A Space Odyssey. Another film, Seconds, starring Rock Hudson, was so brain busting, it kept Brian Wilson away from movie theaters for 15 years! Other than that, films tended to be either straight or artsy-fartsy avant garde. Roger Corman drug culture movies made stabs at being transcendental, but weren't particularly deep, they were mainly just trying to look hip. The television provided most of the mind blowing via The Twilight Zone, The Outer Limits and Doctor Who.
The 1970's was perhaps the worst decade for trippy films. After Easy Rider, things tended to be gritty and realistic.... there wasn't much room for science fiction mind games. Sure, there was A Clockwork Orange and Solaris, but that was just about it. When Star Wars came around in the latter part of the decade, there was no hope whatsoever for mind blowers - science fiction had to be swashbuckling adventure. Giant black obelisks on the moon were out; lightsaber duels were in.
Of course, the 60s and 70s had tons of great mind blowing fiction published during this time, which makes it a bit surprising that none of it never made its way to film.

The 1980's weren't much better. Still heavily influenced by Star Wars, science fiction had to be exciting, not mind blowing. E.T. didn't help matters either. Eraserhead is by far the biggest mind blower to emerge from this decade, with The Wall, Repo Man and Blade Runner trailing far, far behind. It wouldn't be until well into the 1990's that we'd get a flood of mind blowing goodness to movie theaters.
I can't begin to list them all, but among the most notable are: The Matrix, Eternal Sunshine of the Spotless Mind, Primer, The Man from Earth, Donnie Darko, Oldboy, The Fountain, Mulholland Drive, Martyrs and, most recently, Inception.
What the hell? Why all of a sudden? It's not like CGI is necessary to make a mind-blower. Why are we suddenly inundated with these films? I can tell you both Donnie Darko and Martyrs made my cerebrum convulse for days.... I literally felt like I'd taken a severe blow to the head.
In summary, the seventies and eighties produced some great films. I'd much rather watch the gritty realism of Dirty Harry or One Flew Over the Cuckoo's Nest than just about anything. But, when it comes to making movies that hurt the brain, there's been no better time than the present.