One non-Christian view of God is that held, in different ways, by Unitarianism and Islam. This is the idea that God has a unity as one person and which denies the deity of Jesus and the deity and personality of the Holy Spirit.
Deism sees God as out there somewhere (transcendent) and having once acted as creator is not further active in earthly affairs (immanent).
Pantheism goes the other direction. It sees God in all that exists and all that exists in God.
Polytheism is any religious system than contains more than one god. Hinduism is an example. So are the various pagan religious ideas that occur all over the world.
Buddhism has at the center of its beliefs nothingness (Nirvana).
Other systems of thought that do not contain a God are Agnosticism which believes that God is either unknowable or unprovable, and Atheism and various secular ideologies which deny the existence of God.
There are belief systems that have their roots in Christianity but whose ideas are not orthodox. These beliefs are rejected by implication in the Nicene Creed.
These beliefs are not alternate paths to God as some people think. I believe they lead people away from the true knowledge of the triune God.