Q. If Jesus is the second person of the Trinity, isn’t he then equal to both the Creator and the Holy Spirit?
The answer to your question is yes, with a couple of qualifications.
First—and I don’t think this is what you were saying, but just to be clear—it is not the case that Jesus was a human being who somehow became divine and was welcomed into the Godhead. Rather, the second person of the Trinity came to earth as a genuine human being in order to become our Savior. To put this in theological terms, we should have an incarnational Christology, not an adoptionist Christology.
Second, since all three persons of the Trinity are involved in every action of the Godhead, we do not distinguish the persons of the Trinity by their activity. The Son and the Spirit are the Creator just as much as the Father. (At the beginning of Genesis, we see the Father creating by speaking, that is, by the Word, as the Spirit hovers over the unformed creation. So they are all involved. John tells similarly us at the beginning of his gospel, “In the beginning was the Word, and the Word was with God, and the Word was God. He was with God in the beginning. Through him all things were made; without him nothing was made that has been made.”)
Rather, we distinguish the persons of the Trinity by their relationship to one another. The Son is begotten by the Father, but he is eternally begotten, meaning, in the classic phrase, “there was not when he was not.” How this works is a mystery, but it is part of the larger mystery of the Trinity, in which three are one.
The Spirit proceeds from both the Father and the Son. Christians are generally agreed about this; the only disagreement is a historical one about how the Nicene Creed was changed in the Western church to say about the Spirit “who proceeds from the Father and the Son,” rather than just “who proceeds from the Father,” which was the original reading. The Eastern church was in agreement with the doctrine, but it felt that only an ecumenical council (that is, a council of the whole church) could change a creed that such a council had created in the first place. The Western church, for its part, felt that the pope had the authority to add the words “and the Son.”
But that is a matter of how doctrine is to be expressed authoritatively that the larger church is still working out. As I said, there is no general disagreement about how the Spirit relates to the Father and the Son.
So, to summarize, yes, Jesus, the Son, as the second person of the Trinity is equal in power, glory, dignity, and divinity to both the Father and the Holy Spirit. It is marvelous to consider how a person who was so fully God was willing to come to earth in human form, share our experience here, and become our Savior. As the book of Hebrews says about Jesus, “Since the children have flesh and blood, he too shared in their humanity so that by his death he might break the power of him who holds the power of death—that is, the devil. … For this reason he had to be made like them, fully human in every way, in order that he might become a merciful and faithful high priest in service to God, and that he might make atonement for the sins of the people.”
This is the marvel that we celebrate at Christmas time.