In the ancient temple at Jerusalem, Levitical priests sacrificed animals as sin-offerings in expiation for the people's sins, and for the restoration of peace with God.The death of Christ"because it is the death, not only of a man in his created human nature, but also of a man whose Person is the very Son of God himself"far surpasses these ancient sacrifices, which were only a dim foreshadowing of the sacrificial death of Christ.The sacrifice of animals could not take away sin, but could only remind people that they needed to repent of their sins, asking God for forgiveness. This was a forgiveness that was, in fact, granted only through the sacrifice of Christ on the cross; a forgiveness that applied to all sins, those which preceded as well as those which followed upon the sacrifice of Christ.
It is, in fact, this offering of his life on the cross, which essentially constitutes Jesus as priest, our great high priest."Every high priest is taken from among men, and made their representative before God, to offer gifts and sacrifices for sins" In the same way, it was not Christ who glorified himself in becoming high priest, but rather the one who said to him:'You are my son; this day I have begotten you'; as he says in another place:'You are a priest forever, according to the order of Melchizedek'" (Hebrews 5:1, 5-7).
Yes, Christ is our priest, our high priest, called a high priest because it is his own priestly offering that is given to the Father, his unique sacrifice of his life on the cross, offered in atonement for man's sins, and in reparation, to the honor and glory of God.
All other priests are lesser priests than Christ in the sense that, while they are ordained to offer Christ's sacrifice sacramentally, they do so as having received this power from the priesthood of Christ, which he gave to his Church, beginning with Peter and the other apostles, which they then handed on to their successors.Yet, when ordained priests in the Roman Catholic Church exercise their priestly power, e.g., offering Mass, they exercise the same priestly power as that of Christ himself.