Inventor does allow importing of creo asm/prt files.. BUT like any software it can only open creo files from 1 version or later back from the current version..
So Inventor 2013 can open creo 2012 and back files.. 2014 Inventor can open creo 2013 and back files.. "usually" anyways..
You also have the option of exporting to a neutral format like step/iges from creo and importing those into Inventor.