I like scifi that doesn't try to have some big over-riding moral or anything. Avatar was good but I pretty much ignored the moral behind the story. I thought about it afterwards of course, but during the movie I just want a good plot, good acting, lots of action and good believable effects.
I don't think movies have to be "life changing" or even thought provoking to be good. Star Wars wasn't. It was just cool, with different worlds, and different creatures, and action and stuff.
A lot of movies today think that they need to have some big moral or else they are just driven by special effects.