There's a difference in quality here. The widow's son, Lazarus, and the dead girl were all raised from death back to a continuation of mortal life. They would live out their remaining time and eventually die (again) and be buried.
Resurrection is something different entirely. Jesus was raised from death to immortality. In Luke chapter 24, when Jesus appears to his disciples, they're afraid, thinking they've seen a ghost, but he reassures them that he's a fully tangible person and describes the makeup of his body with the unique phrase "flesh and bones". This contrasts strongly with the more common "flesh and blood," and suggests that although his resurrected body may have looked recognizably like the Master they knew before he died, it was not made from all the same stuff that our mortal bodies are made from.
It was this fundamental change, not having been restored from death back to mortal life, but resurrected, from death forward to immortal life, that showed Jesus's divine nature. While other passages of scripture, such as the 5th chapter of Revelation, speak of the general resurrection of the dead, showing that this miracle is not confined solely to Christ, the rest of the dead will be raised through the act of an external agency--by the power of Christ--but Jesus, being divine, did not require an external agency:
17 Therefore doth my Father love me, because I lay down my life, that
I might take it again.
18 No man taketh it from me, but I lay it down of myself. I have power
to lay it down, and I have power to take it again. This commandment
have I received of my Father.
-- John 10: 17-18, emphasis added
