If you convert from Christianity to Buddism, Shinto, Hindu, or even Norse mythology you would be worshipping other gods.
Islam is a rewrite of portions of the Judo-Christian texts but there are radical differences.
Islam is an antichristian (as in antiChrist, not necessarily "AntiChrist") religion because it ignores and changes the role of Jesus to a liar and prophet. It does this to lead followers to another prophet.