There are a few fatal issues with your post.
1. In Christianity, Satan is not a person, but rather the personification of temptation whose purpose is to tempt humanity to the path of idolitry. In earlier Jewish texts, Satan was the adversary of humanity, a prosecuter of humanity before God.
In most religious faiths, Christianity, Daoism, Buddhism, etc... They focus on a way to enlightenment. It is presented differently in different cultures, but is ultimately the same philosophy. Enlightenment is reached through a total rejection of idolitry (Or a devotion to earlthy objects). The force which tempts idolitry in Christian philosophy, as I mentioned above, is called Satan. Since The Way opposes idolitry, there is a logical opposition to temptation to idolitry. So Christianity opposes Satan for this reason.
2. The bible wasn't written by God, it was compiled by Christians in the 3rd through 5th centuries who compiled various manuscripts written by mystics who followed the way; 21 of the books in this compilation were canonized as religious scripture during the reign of Constantine in the 4th century, with six more additions later. There is also no reason you should attribute any of the writings to God since none of these manuscripts are in any way said to be written by God. Some of them are accounts of the life of Jesus (Gospels attributed to John, Luke, Mark, and Matthew), accounts of the doings of the Apostles (Acts, attributed to Luke), letters written to discuss the way (Pauline letters, obviously attributed to Paul), and metaphorical works meant for the purpose of divination (Revelation, attributed to John). On top of these books which were canonized, there were hundreds of others which were not.
3. In case you didn't gather it from point 2, the Bible isn't a single book. Rather, it's a collection of books from multiple traditions gathered between the time of Marcion of Sinope and the 5th century AD. Satan factors into many of these traditions, most prominently into Revelation.
4. The reason why "Satan" doesn't appear in other religions is because of etymology rooted in the Hebrew language, and philosophy rooted in Christian culture. Other religions have other representations rooted in other cultures, and other names rooted in other etymologies. For example, Buddhist tradition has Mara who is the Buddhist equivalent of Satan.
You should really post more often in these types of threads ;)