(2) In the last 26 sonnets, the object of affection is a dark lady. In traditional Renaissance poetry, the beauteous lady is presented as blond-haired and blue-eyed. Moreover, she is typically virtuous and pure. Shakespeare's lady not only has dark hair and dark eyes, but she is also sensuous and sexually promiscuous (or active). Thus, lust (rather than virtue) becomes a more common motif in these sonnets.
(3) In the sonnets by Petrarch and Sidney, the focus is primarily on the speaker as an unrequited lover. And so the poems reflect the up-and-down emotions that the speaker experiences as he goes from hope to melancholy or from delight to disgust. There is no unrequited love in Shakespeare's sonnets, and the poems do not reflect the see-saw (the up-and-down) emotions of the speaker. However, Shakespeare's sonnets do indicate several conflicts within the speaker.
(4) There is, perhaps, more of a story (although it is rather vague) in Shakespeare's Sonnets than in other sonnet cycles.
