I don't know if it is selfish, but it is taking the Lord's name in vain. If you take the Lord's name in vain, you are violating God's commandments.
One more thing: There is only one God. There is no other. He is the God of Abraham, Isaac, and Jacob. His son is Jesus Christ. The third person of the Trinity is the Holy Spirit (Yes, I do believe in the Trinity).
If you worship any other gods, they are false gods. That means you have an idol. The King James Bible is very clear that idolatry is a sin. Idolaters are going to end up in Hell.