I was a hardcore Star Trek geek as a kid. Who wasn't, really? Captain Kirk going all maverick on the galaxy, finding cool new planets, and nailing hot alien babes. Space is cool! I think I watched every episode at least a couple dozen times - yay syndicated reruns - but for some reason it's the first motion picture version of the franchise (released in 1979) that really affected me.
Holy crap. The Voyager space probe, damaged and worn. And pissed off, looking for its creator.
So, we fire off some probes into space. We don't have the technology to really track them, or communicate with them. 300 years later, one is found by a mechanical civilization, and taken in as an injured entity. Repaired, as well as it could be, then sent home. Hindsight makes it pretty clear that this is at least the precursor to the Borg storylines - mechanical civilizations, attempts to communicate with them, etc...
It brought up all kinds of issues that have nothing to do with science fiction - do we have a responsibility to the things we create? What does it mean to be "the creator"? What does this mean with respect to religion, theology and belief in general?
The effects in the movie are completely laughable - the psychedelic optical effects are stunningly lame compared to the film resolution digital effects of today - but the premise of the movie struck me as profound. Our actions have consequences - they may be far in the future, far away, in ways unimaginable to us now, but our actions have consequences.
Of course, the movie franchise has been mind-blowingly inconsistent. Basically, the even-numbered movies were pretty good (KHANNNNNNN!!!!! KHAAAAAAANNNNNNN!!!!!!!), the odd-numbered movies pretty much sucked, but they all feel like bubblegum pop filler. V'Ger was a game changer though.