Well, if it's 'most perfect' rather than 'greatest' -- the former being a slightly more interesting parlor game than the latter -- I would nominate Philip Sidney's Horatian Sapphics from the Arcadia:
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If mine eyes can speak to do hearty errand, Or mine eyes' language she do hap to judge of, So that eyes' message be by her received, Hope, we do live yet.
But if eyes fail then, when I most do need them, Or if eyes' language be not unto her known, So that eyes' message do return rejected, Hope, we do both die.
Yet, dying and dead, do we sing her honour; So become our tombs monuments of her praise; So becomes our loss the triumph of her gain; Hers be the glory.
If the spheres senseless do yet hold a music If the swan's sweet voice be not heard but at death, If the mute timber when it hath the life lost Yieldeth a lute's tune,
Are then human minds privileg'd so meanly As that hateful Death can abridge them of power With the vow of truth to record to all worlds That we be her spoils?
Thus, not ending, ends the due praise of her praise: Fleshly veil consumes, but a soul hath his life Which is held in love: love it is that hath join'd Life to this our soul.
But if eyes can speak to do hearty errand, Or mine eyes' language she do hap to judge of, So that eyes' message be of her received, Hope, we do live yet.
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Michael J. Smith mjs at smithbowen.net
http://stopmebeforeivoteagain.org http://www.cars-suck.org http://fakesprogress.blogspot.com