Well, it all depends on your game how things are handled. Usually game entities or particles will be self-directed. The bad guys in the Pac-man maze are probably sprites with their own code that uses timers to call them back at intervals so that they can decide where they're headed and whether they need to alter direction, etc based on their location in the maze and their preternatural knowledge of which way you're going. The scrolling surface you're flying over on Xevious could be a simple movieclip loaded playing in the background.
Two good places to start looking at how you might organize things in PureMVC would be the AS3/HelloFlash Demo (see the HelloSprite) and the AS2/Balloonatroid demo.http://trac.puremvc.org/Demo_AS3_Flash_HelloFlashhttp://trac.puremvc.org/Demo_AS2_FlashLite_Ballonatroid