It's a weird gray area, there; as I was thinking about Crichton long and hard with those comments.
Jurassic Park truly straddles the line; as much of the science is pretty good science--in that it reflects upon very real, very serious scientific thought at the time, it is widely known to be pure fantasy (the method of harvesting DNA from amber, and replacing with nicked bits with modern frog DNA is, completely, impossible--rather, it would amount to nothing).
However, these projects existed, and where only shown to be the stuff of fantasy after several attempts. Crichton is good stuff, in the end, as his work appeals to real science and expands upon very real possibilities, current thought, and extracts from this engaging, self-reflective, and socially-aware themes.
Dickens is fiction; doesn't mean his work isn't impossible. True Sci Fi understands this distinction, and simply pulls from different resources.