The Best of the Renaissance is certainly worth buying if only for the amazing "Spem in Alium" by Thomas Tallis.Nevertheless, I do not share the boundless enthusiasm of other reviewers for this album.
To begin with, three Masses are featured on this album,two on the first cd. That is too much to my liking. And while the Mass Pange Lingua by Desprez is undoubtedly a wonderful piece, the other masses are not the best: the Mass for five voices by Byrd, while very beautiful, lacks the depth, emotion and intimacy of his Mass for three voices. The Missa Papae Marcelli by Palestrina is brilliant but nothing more than an academic exercise in virtuosity.
And I definitely do not appreciate Gesualdo's Tenebrae Responsories for Holy Saturday. This is simply very mediocre music that nobody would care for if it did not sound modern in its cerebral ugliness and thereby flatter our infatuation with ourselves.
I recommend "The Essential Tallis Scholars" either instead of or in addition to "The Best of the Renaissance", depending on your pocket and interest for Renaissance choral music. I would also recommend O Magnum Mysterium by the Robert Shaw festival singers. Although only a third of that album is devoted to Renaissance music, the interpretation is so beautiful and spiritual that it is really worth having in your Renaissance music collection.