Well IMHO, Bush was likely right about those three countries. Iraq was / would be up to no good no matter what. (We've smashed the status quo there and changed the dynamic, hopefully for the better.) Iran will either be undone internally or will ultimately become a threat to the world, since they have shown a willingness to support extremist groups. North Korea - who the hell knows what they're up to, but we do know they have nuclear weapons.
If we had stable democracies in all three of those regions, the world would be a much safer place for all involved.