In Star Trek Generations, during Picard's Nexus fantasy, he is seen with a wife and children. I think a cool touch and missed opportunity would have been having his wife in that fantasy be Jenice Manheim. Jenice was his great lost love featured in the season one episode "We'll Always Have Paris". The episode itself is not great, but it would have been a nice touch, as it might make sense that if Picard had chosen to be a family man, he might have settled down with his great lost love Jenice. Just a subtle reference would have been enough, it would have satisfied the diehard trekkies without adding info that might confuse more casual fans unaware of that lore.
I also don't understand why Kirk's ideal fantasy was him puttering around a farm and chopping wood. Wouldn't his spot of bliss be doing what he knew and loved best and commanding a starship or fighting some alien on some harsh planet surface?
So I think what the nexus does, based on the evidence, is not provie the ultimate fantasy, but rather gives users a view at potential alternate realities had they made different choices in their life. It's a sort of correct-your-regrets or grass-is-greener simulation device.
I'd love to have seen what Soran's and Guinan's experiences were while in the nexus, but we can only wonder.
I think the nexus is an artificial construct rather than a naturally occurring anomaly. Essentially some form of super-advanced holodeck likely designed by an ancient and advanced civilization. This is an aspect I would have like to have seen addressed more--the actual nature of the nexus, but instead it's just used as a convenient plot device and no one in the film ever tries to understand its nature--that seemed contrary to how the crew would've approached it if this had been an episode of the series rather than a movie. But being a big action movie, they had to focus more on the big villain and ignore the interesting scientific and philosophical implications of the situation. This is characteristic of where most of the ST films have gone wrong--providing dumbed down space opera because the writers and producers assume that audiences don't want to think too much. Which may be true, given how many people consider The Motion Picture to be the worst Trek film.
