Conversely, its possible to believe in religion without believing in God, Like Buddhism (or non-theistic satanism, but thats another story) I think it also depends on how you define 'religious'.
My view is that man is religious by nature. Those that dont believe in God will still celebrate christmas or buy easter eggs for their kids (I know they arnt originally christian festivals). But mankind has a need for ritual, whether you see it as religious or not is neither here nor there, its still ritual.
In the courts we still have the 'ritual' of swearing on oath and judges and barristers wearing horse hair on their heads.
We have certain days set aside for certain celebrations, eg. Bonfire night, halloween, valentines day etc.
People 'religiously' (or ritually) watch every episode of the x factor or Eastenders.
My point been that you can believe in God but we cant help BUT been religious.
*RUNS AND HIDES FROM THE BAYING MOB*