Well first off if you aren't a fan/player of the games on which this is based you probably won't be drawn to this movie BUT I say fan or not give it a try.
First thing that will strike you is the visual presentation. Now there has been a lot of CGI generated animation as of late, all of a great visual style e.g. Shrek, The Incredibles, and Madagascar this is no exception. First of all look at the opening shots of a city, with traffic and crowds of people and take a second or two to think of just how many figures there are on screen that they have animated at one time!
Detail is crystal clear, and the animation smoother than smooth. If Spirits Within put you off, then please don't let that deter you.
Okay so the storyline may be puzzling for none fans but you can follow it and well, prepare for a visual treat if nothing else.
There are flashback scenes and what's more useful is in the extra material, is a look back to the game itself, and that will help fill in the gaps as far as the story goes.
Go on give this a try.