The Easter Vigil is the “mother” of all Vigils. This is what Paschale Solemnitatis says on the matter:
A. The Easter Vigil
- According to a most ancient tradition, this night is “one of vigil for the Lord,”  and the Vigil celebrated during it, to commemorate that holy night when the Lord rose from the dead, is regarded as the “mother of all holy vigils.” For in that night, the Church keeps vigil, waiting for the resurrection of the Lord, and celebrates the sacraments of Christian initiation. 
- The Meaning of the Nocturnal Character of the Easter Vigil
- “The entire celebration of the Easter Vigil takes place at night. It should not begin before nightfall; it should end before daybreak on Sunday.”  This rule is to be taken according to its strictest sense. Reprehensible are those abuses and practices that have crept into many places in violation of this ruling, whereby the Easter Vigil is celebrated at the time of day that it is customary to celebrate anticipated Sunday Masses. 
Those reasons that have been advanced in some quarters for the anticipation of the Easter Vigil, such as lack of public order, are not put forward in connection with Christmas night nor other gatherings of various kinds.
- The Passover Vigil, in which the Hebrews kept watch for the Lord’s passover which was to free them from slavery to Pharaoh, is an annual commemoration. It prefigured the true Pasch of Christ that was to come, the night that is of true liberation, in which “destroying the bonds of death, Christ rose as victor from the depths.” 
- ***From the very outset, the Church has celebrated that annual Pasch, which is the solemnity of solemnities, above all by means of a night vigil. For the resurrection of Christ is the foundation of our faith and hope, and through baptism and confirmation, we are inserted into the paschal mystery of Christ, dying, buried, and raised with him, and with him, we shall also reign. 
The full meaning of Vigil is a waiting for the coming of the Lord. ***
It is perhaps the culmination ouf the Paschal Triduum. Now, this is not to say that Easter Sunday is not important; however, it is on the night of the Easter Vigil that we hear the Gospel account of the Resurrection story.
It is one of the most, if not, the most, beautiful liturgy of the year. It also completes the Paschal Triduum. As I understand it, the whole three Days are to be taken as one complete liturgy that begins on Holy Thursday, the Evening Mass of the Lord’s Supper, and ends with the Easter Vigil. That is why you don’t have a concluding rite on Holy Thursday and you proceed in unbroken silence to Good Friday. Good Friday has no concluding rite and you go forth to the Easter Vigil on Holy Saturday.