My take on this is that fantasy is merely what is not real now. You may be fantasizing that you're uber rich but unless you act on that by setting goals, it remains a fantasy.
Obviously some fantasy would never become a reality, no matter how hard you try to. In certain cases, you might have to settle for something else. You can't fly with wings but you can try becoming a real life Ironman (which in itself already require a lot of resources to translate to reality).
Science fiction inspires reality. Many technologies we have now were fantasies of people in the past. They'd probably be giddy to see an Apple watch. People first fantasize about stuff and then they try to see if it's possible. Many people have fantasized about teleporters and now people are busily looking at spooky action if that might make it come true.