One reason, among many others, to believe the New Testament's resurrection accounts is their restrained nature. Nobody narrates Jesus' resurrection. Or the appearance to Peter. Or the appearance to James. If anybody narrates the appearance to more than five hundred people (1 Corinthians 15:6), he does so without mentioning that so many individuals were involved.
It's often pointed out that there are some elements present in the resurrection accounts that are unlikely to have been fabricated (females, including one as disreputable as Mary Magdalene, as the discoverers of the empty tomb and the first to see the risen Jesus; the initial unbelief of the male disciples; etc.). We should also note how what's absent often provides us with evidence for the accounts.