Currently I am under the conviction that other “gods” exist. Ra, Zeus, Odin, etc. may all (or all have) exist(ed at one time) in my opinion.
BUT they are far, far different from YHWH, the God we worship.
First of all, they are not omnipotent like our God. Poseidon might have some influence over things of the sea, but he is (if he exists) impotent on the land, for example. Only God controls land and sea and sky, and everything else.
Second, at least some of them (according to the myths) are not everlasting either. I cannot speak for the Greek gods as dying, but I can say that Athena was borne of Zeus’s skull (meaning she has a beginning. But Osiris was once killed (IIRC). In Ragnarok, the Norse gods will (or have?) all die(d). God is, of His nature, incapable of dying.
Thirdly, they, unlike God, are morally imperfect. Zeus, for example, was often guilty of adultery (which Hera/Juno chastised him for), as was Aphrodite. Often the Greek gods were fighting amongst each other, as they could not come to an agreement on who or what was a good cause and what wasn’t. (The Iliad and the Odyssey, or example, tell stories of the battles between different factions of gods.)
Fourthly, in Acts there is an altar in Athens to an unknown God. Paul spoke of this god as the Lord God, ours. If I understand correctly, this unknown God was not merely a placeholder, but the God even “the gods” turned to for guidance.
So who might “the gods” be, then? Figments of the imagination? Possibly. Bel was, as was Ba’al.
I believe, however, they are fallen angels that sought and seek to be worshiped in place of God. Perhaps they really did have power over some parts of the world (like the sea, or the harvest). BUT their power is or was nothing compared to God Almighty, who has the power not only to calm the seas or bring the sun to us day after day, but also to give us life for ever and forever. And God lives forever and ever.
No other “god” can claim to be all that God is. If they do indeed exist, no other god compares to Him at all.
Am I wrong in believing other gods exist, even if they are powerless compared to God Almighty and not worthy of worship? They are, after all, dependent on God for all their power (just as Satan is; he would not exist unless God allowed him to).