That makes sense

First, about worshiping on Sunday: The reason that Christians worship on the first day of the week goes back to the beginning of the faith. The idea is that Christ's Resurrection began a New Creation, and so we worship the Creator on that day.

Second, it depends what you mean by "sun god". If, by that term, you mean a being above whom there can be no other, who has no beginning or end, from whom all things come... then that is the One God mentioned in Scripture, even if it is an imperfect or unclear idea of God. Many of the ancients saw that if one being was referred to as a god among other gods, than that being was not all powerful and could not be worshiped, but that if we are to worship a divine being, it must be beyond our comprehension and not simply an exalted man.

Man can, however, know that there is a Creator by his own intellect, and this is how and why so many ancient cultures had similar concepts of a single creator god. Unfortunately, because our intellect is limited we can only know so much by reason alone, and so we see that addition of a wife and children of this creator god and the God of the Universe then becomes one among many.

A potential objection to this is that Christians worship Jesus as the "Son of God", but what we mean by this is far different than what was meant by Thor being the son of Odin. When we refer to the Triune God, Jesus is begotten by the Father and not created or made, and the love between them begets the Spirit... but all three Persons exist as one God, or the Trinity

Zeitgeist is cancer. I literally groan every time someone comes out with a "herp derp Jesus is Osiris/Horus/Gozer" post.