Does anybody know the name of a Sci-fi movie starring someone like Kurt Russell (but it's not him) in which a man is guardian to a boy on a future Earth where aliens have enslaved the human race and most humans are imprisoned in caves? That's all I remember...

Sounds a little like

Planet of the Apes (2001) (http://www.imdb.com/title/tt0133152/)

Or Planet of the Apes (1968) (http://www.imdb.com/title/tt0063442/)

It's a john travolta movie, he is one of the ape guys. Name is battlefield earth.