Perspective plays a large role in The Tempest. The island is dominated by magic, and it clouds the ability of all the new arrivals to tell the difference between reality and the magical illusions they see. Reality is also tempered by the outlook of the individuals – Gonzalo is relentlessly positive, and so sees the island as beautiful. Ariel revels in the island's naturalness, while Sebastian and Antonio see it as an inhospitable place because of their negative outlooks. Reality is clouded by magic, and this duality is only furthered by the influence of personal perspective over each individual's perceptions.
People construct their own versions of reality depending on their perspective. The influence of magic in this play is irrelevant, because the characters' divergent interpretations of reality are due to their different experiences and perspectives.
Antonio and Sebastian are unrealistic characters because they have absolutely no remorse or fear of accountability.