The ultimate reward of the three was that they would have “fulness of joy; and … shall sit down in the kingdom of [the] Father.” That is indeed a marvelous blessing, but it must be remembered that it is the blessing available to all:
“Thou wilt shew me the path of life: in thy presence is fulness of joy; at thy right hand there are pleasures for evermore” (Psalms 16:11).
“But, behold, the righteous, the saints of the Holy One of Israel, they who have believed in the Holy One of Israel, they who have endured the crosses of the world, and despised the shame of it, they shall inherit the kingdom of God, which was prepared for them from the foundation of the world, and their joy shall be full forever” (2 Nephi 9:18).