Christians theists only care about their faith being a monotheism "the belief in the One God" because monotheism has for centuries been universally understood to be more advanced than polytheism. So, they just call Yahweh "the one and only God" and the other ones, "Christ, Mary and Satan" as "spirits" "angels" or "one with Him." Its just a play on words.
In my work, I call it "a semi-monotheism" inorder to be accurate and at the same time, fair.
brough
http://civilization-overview dot com
I think it would be more accurate to say that throughout Christian history, and prevalent among the largest segment of the Christian population today, is the belief in the Trinity, and that Jesus is the Son of God. Their belief does not place Mary, the saints, angels or Satan at the status of the godhead.
Obviously that leaves non-believers noticing that Christians seem to equivocate, or as you say, it's a word game.
What is missing from the general Christian system of belief is the connection it has with other world religions of the time, that influenced its development. Christians will readily acknowledge that their beliefs are influenced by Judaism, while at the same time disputing that Judaism is the true religion.
For anyone who looks a little deeper, the roots of Judaism are traceable to other ancient religions of that time and place. One such infusion of outside beliefs happened to be taking place in Judaism at the time the story of Jesus sprang up. This is why Christianity shows not only ancient traces of polytheism originating through Judaism, but other polytheisms contemporaneous to the writings of the New Testament, and among these are the rise of notions of angels and devils, Mary and the saints, and a host of other innovations to Judaism, such as resurrection of the dead, last judgement, and eternal reward in heaven. These are foreign concepts, imported from neighboring religions, such as Mithraism. The Son of God is an archetype prevalent in the religions of the region.
For me, it is not a word game, although many folks who post here do like to play word games.
For me, it boils down to understanding a few basic ideas from history and archaeology, that there is no "true" religion, since religions evolved, belief systems bumped into one another and either absorbed one another's archetypes, or created anti-archetypes to oppose them.
So to best deal with this question, a Christian ought to learn about the origins of Christianity--not from a biased source--but from a scientific one.
Incidentally, this question plagued ancient Christians and became the basis for numerous bans against heretical doctrines, and for the centralization of the authority for Christianity in Rome (before the schism), and for the Protestant use of the term "Catholic" as an epithet, as it is often used today. For perhaps 1500 years the term merely referred to the central belief that abhors heresies like anti-Trinitarianism or the non-divinity of Jesus. Furthermore, although Protestants often claim they have purged their religion of inventions added by Catholics, this claim demonstrates an ignorance of history. Catholics were the first Christians--the authors and caretakers of the scriptures Protestants hold sacred.
I add this to the list of Christian fallacies: that Protestants have built a belief system based on not only one, but two beliefs they claim are false: Catholicism and Judaism.
Also, there is nothing new in this issue of reconciling the Trinity with monotheism, or that Jesus was God incarnate. Such doubts arose as soon as the Jesus story sprang up. It's just that we have the advantage of perspective, to understand these beliefs in the context of history.