I have read that Crete produced some of the best quality archers in the ancient Mediterranean, what was it that set them apart from other archers of the time?

Mostly the fact that they were Cretan. I've written about Cretan archers at length recently - see here. While Cretans were known to specialise in ranged combat due to the rugged nature of their homeland, their reputation as mercenary archers was largely self-sustaining. Cretans offered their services as mercenaries; since Cretans were available, those looking to hire archers would hire Cretans; the Cretans therefore became widely known as useful mercenaries, increasing demand; the Cretans realised that service abroad was a good way to make a living, and offered their services; and so on. Effectively, the Cretan archer was a brand. While skilled use of the bow certainly took a lot of practice, there is nothing in the literary evidence to suggest that Cretans had special skills that others couldn't replicate.

The Cretan archer would likely have been indistinguishable from other Greek light infantry in dress and equipment. They would wear tunics, but no body armour; on their heads they might wear a felt cap or a loose wide-brimmed sun hat. Their bows were probably short composite bows, expensive and delicate; the maximum range of these bows was perhaps 150 meters, their lethal range much less than that. Those who could not afford composite bows would have used simple bows with a smaller effective range. Xenophon once mentions that the Cretans of the Ten Thousand carried small bronze shields, but it is difficult to picture how such a shield would be wielded by an archer. Either some of the Cretans with this army were not in fact archers but peltasts, or they carried the bronze shields purely for the occasion Xenophon is describing (they were meant to flash their shields in the sun to make the enemy think there was a large force waiting in ambush).

The only distinctive feature of Cretan archers was that they sometimes used arrows with very large bronze tips. These were so much larger than the average arrowhead that it is difficult for archaeologists to distinguish between Cretan arrows and the bolts of the gastraphetes or belly-bow, the earliest piece of proto-artillery. However, I can't think of any scholarship that has examined the impact of this large arrowhead on the Cretan archer's range and potential armour-piercing capabilities.