The lack of article and the preposition PROS signals that QEOS is generic in a grammatical sense. Because of the nature of the word and because another QEOS is mentioned, I draw the conclusion that it also is generic in the semantic, uncancelable meaning.
Monotheists therefore worship only one god, polytheists more than one.
Monotheism or polytheism depends on how one views the relation between the Word and the Father. I disagree with Will that John used the Platonic setting, but this setting was used when the church Fathers made their dogmas. As a matter of fact, all the church Fathers before Nicaea entertained the view in some form that the Son was subordinated to the Father. There is hardly one book in the NT which more clearly differentiates between the Father and the Son than the gospel of John. I do not suggest that QEOS has a double meaning in this passage or elswhere.