Say what you want about Strieber, but I love his idea that they are interested in new ways of thinking.
Consider a species that has developed beyond material need, and can travel and bend the universe to it's wishes. It may have also answered all the questions that it's mind is capable of asking.
What would it want next?
To understand new ways of thinking, perhaps. Think of V'Ger... needing to transcend itself to ask new questions. Our newness and naiveté may be exactly what they're interested in.
I remember something Whitley wrote, that one day he tried to formulate a question in his mind for the Visitors; he wanted to know the way they looked at the Universe.
An image appeared on his head. The image was that of a closed coffin.
That was a very interesting idea, to think how an intelligence that may be incredibly ancient, that has learned all there is to know about the Universe, and may have even solved the problem of Death itself, would see reality as a prison from which there is no escape --so yeah, your mentioning of V'Ger is right on the money in my book
It made me think: Perhaps what they seek in us is
Novelty: The chance to re-experience the thrill of discovery in a younger species. The same way a parent gets to experience the wonder of Xmas & Halloween by proxy through his children, the joy of seeing your son or daughter take its first steps, or to see the look in their eyes the 1st time you let them watch Star Wars.
Of course, you could also see it from
another perspective, like when you see some old fart dating a beautiful girl 20 or 30 years younger than him, and you know he's using her in order to feel young again, as some sort of creepy vampire.
Patient parents or creepy vampires? I admit the jury is still out with regards to the Visitors & their intentions.