Using Creo View, I have learned that it will open Gerbers and display them just fine, however I learned from a support tech at PTC that it is not possible to load several Gerbers into the same session and overlay them. Examples of products that CAN do this are "ViewMate" and "DFM Now!". Both of these products will allow the user to import an entire directory of Gerbers and overlay them, then selectively use the tool to turn 'layers' on and off for comparison or to review ECAD gerbers for a multi-layer PCB.
This seems like functionality that should already be in the tool, (and maybe it is, but the tech doesn't know it?) so I'm hoping it is considered for future versions of Creo View or Creo View Lite.