Question: Who saw Jesus first?
(MATT28:9)Jesus makes his first appearance to the Mary's
(MARK16:9) Jesus makes his first appearance to Mary Magdalene only
(LUKE24:15-18) Jesus makes his first appearance to Cleopas and another
(JOHN20:14) Jesus makes his first appearance to Mary Magdalene only
(1COR15:5) Jesus makes his first appearance to Cephas (PETER).
Response: Who saw Jesus first? I would say that Mary Magdalene was the first person to see the risen Jesus. I base this on Mark 16:9 because there it specifically says that Mary Magdalene was specifically the first person to see the risen Jesus. John 20:14 is consistent with this opinion. And, Luke 24:15-18 and 1 Corinthians 15:5 don't specifically address the issue of who was the first to see the risen Jesus. I also speculate that the other Mary was the second person to see the risen Jesus, based on what I believe is a "compressed" or "telescoped" account given in Matthew 28:9. So let's take a look at each of the verses and see how they compare in regards to who first saw the risen Jesus:
In Mark 16:9, it says that Jesus first appeared to Mary Magdalene. Mark doesn't mention the other Mary or anyone else. But Mark never claimed specifically that Mary Magdalene was alone. All that we can know for certain is that Mark 16:9 is claiming that Mary Magdalene was first. Nothing more, nothing less.
In Matthew 28:9 it says that Jesus suddenly met "them" sometime after they had learned that Jesus was not in the tomb. I assume that the "them" includes Mary Magdalene and the other Mary because they are specifically named in Matthew 28:1. Matthew makes no distinction as to whether Mary Magdalene saw the risen Jesus first or if she and the other Mary saw Jesus at the same instant. So, it is possible that Mary Magdalene actually saw Jesus first and that the other Mary saw him soon after that. That would be consistent with Mark 16:9. However, perhaps Mark 16:9 only chose to focus solely on Mary Magdalene and that the other Mary was also present.
Any claim that there is a contradiction between Matthew 28:9 and Mark 16:9 would be based on speculation.
Luke 24:15-18 explains that the "women" went to the tomb and saw that Jesus was not there. Luke does not specifically identify the women. But, he does say that Mary Magdalene; and Mary, the mother of James; and a woman named Joanna; went to the others to tell them that Jesus had risen. Was Joanna present at the empty tomb? Or did Joanna meet Mary Magdalene and the other Mary as they went from the tomb to tell the others that Jesus had risen? We don't know for certain. Luke doesn't say that any of the women had seen Jesus on their way back from the tomb. However, Luke explains that two of Jesus' followers were on the road to Emmaus, including a person named Cleopas, and that they saw Jesus. But Luke does not say that they were the first to see the risen Jesus. If indeed there is any contradiction, it is based on speculation, not on facts.
John 20:14 says Mary Magdalene met the risen Jesus. But, like Mark 16:9, there is no mention of the other Mary, or anyone else, being present at that point in time.
As for the account given in 1 Corinthians 15:4, there again is no mention of who specifically was the first to see Jesus. And it is obvious that it is in no way an attempt to be a comprehensive list of everyone who saw the risen Jesus. What it does say is this:
1. Jesus was buried,
2. Jesus was raised,
3. Jesus appeared to Peter,
4. And then Jesus appeared to the other Apostles.
All we can know for certain in regards to 1 Corinthians 15:4 is that Peter saw the risen Jesus after Jesus had risen and before the other Apostles had seen him. Nothing more, nothing less.
As you can see from the various Bible verses, some are specific in certain details and others are not. But there is no provable contradiction in regards to which person first saw the risen Jesus. If my opinion is correct that Mary Magdalene was the first person to see the risen Jesus, then that would provide a possible reason as to why Mark and John chose to focus solely on Mary Magdalene.