Deuteronomy 6:4 - “Hear, O Israel: Yahweh our God, Yahweh is one.”

Psalm 96:4–5 - “For great is Yahweh and most worthy of praise; he is to be feared above all gods. For all the gods of the nations are idols, but Yahweh made the heavens.”

Isaiah 43:10 - “You are my witnesses," declares Yahweh, "and my servant whom I have chosen, so that you may know and believe me and understand that I am he. Before me no god was formed, nor will there be one after me.”

Christians worship God exclusively because the Bible makes it clear it is God who ‘created the heavens and the earth’. [Gen 1:1]. As a consequence, if God created all things, then there can be no other god. Any other god that people choose to worship is, in reality, something they have created or dreamt up for themselves.

You'll notice that the gods of the Greeks, Romans, Hindus, and Egyptians all had something to do with creation, such as the sun, moon, and sea. All of these things were made by God himself. As a result, God correctly instructs all people to worship him rather than the things he made. Unfortunately, people choose to ignore God's decree in this matter, and as a result, they will face God's judgement [cf. Romans 1:21-25].