Emotionally investing in other worlds

Regarding his new film, Inception, Leonardo DiCaprio was quoted by the London Daily Star as saying:

This is my first science fiction film.  I have a hard time with science fiction.  I have a little aversion to it, because it's hard to emotionally invest in worlds that are too detached from what we know.

I can only assume that DiCaprio was referring to science fiction films, and not written science fiction.  I, too, find difficulty emotionally investing in much of the science fiction films that ...