Don't get me wrong, I am not claiming that for a system of beleif to be a religion it must have a written doctrine and that a huge population must follow this doctrine to the letter.  If this was the case, the majority of tribal religions would clearly make my statement false since many of them still rely soley on Oral Traditions and havn't written anything down.  Furthermore, tribal religions are specific for a specific tribe meaning that they do not neccessarily feel that everyone should follow their traditions, in fact, each native american tribe, for example, have their own specific creation story for their tribe (as opposed to a creation story for the entire universe).  However, these tribes still appeal to a deity of some sort which they attribute the creation of the earth to (as well as pray to various spirits).  Buddhism however (as well as Toaism) do not really attribute the creation of the world to a deity but rather to a more abstract idea (yes even more abstract than God), Nothingness or Nirvana.  So it is not like they pray to Nirvana or ask Nirvana for mercy or forgivness (or consider Nirvana distant like many Tribal Religions consider the First Father, as some of them call this deity, to be).